Script URL is a form of eval. Open
linkHref = [ 'javascript:void(location.href=\'mailto:\'+',
- Read upRead up
- Exclude checks
Disallow Script URLs (no-script-url)
Using javascript:
URLs is considered by some as a form of eval
. Code passed in javascript:
URLs has to be parsed and evaluated by the browser in the same way that eval
is processed.
Rule Details
Examples of incorrect code for this rule:
/*eslint no-script-url: "error"*/
location.href = "javascript:void(0)";
Compatibility
-
JSHint: This rule corresponds to
scripturl
rule of JSHint.
Further Reading
Script URL is a form of eval. Open
linkHref = [ 'javascript:', protectEmailLinkAsFunction( email ) ];
- Read upRead up
- Exclude checks
Disallow Script URLs (no-script-url)
Using javascript:
URLs is considered by some as a form of eval
. Code passed in javascript:
URLs has to be parsed and evaluated by the browser in the same way that eval
is processed.
Rule Details
Examples of incorrect code for this rule:
/*eslint no-script-url: "error"*/
location.href = "javascript:void(0)";
Compatibility
-
JSHint: This rule corresponds to
scripturl
rule of JSHint.
Further Reading
File link.js
has 1133 lines of code (exceeds 250 allowed). Consider refactoring. Open
/**
* @license Copyright (c) 2003-2013, CKSource - Frederico Knabben. All rights reserved.
* For licensing, see LICENSE.html or http://ckeditor.com/license
*/
Method 'onOk' has too many statements (67). Maximum allowed is 30. Open
onOk: function() {
- Read upRead up
- Exclude checks
enforce a maximum number of statements allowed in function blocks (max-statements)
The max-statements
rule allows you to specify the maximum number of statements allowed in a function.
function foo() {
var bar = 1; // one statement
var baz = 2; // two statements
var qux = 3; // three statements
}
Rule Details
This rule enforces a maximum number of statements allowed in function blocks.
Options
This rule has a number or object option:
-
"max"
(default10
) enforces a maximum number of statements allows in function blocks
Deprecated: The object property maximum
is deprecated; please use the object property max
instead.
This rule has an object option:
-
"ignoreTopLevelFunctions": true
ignores top-level functions
max
Examples of incorrect code for this rule with the default { "max": 10 }
option:
/*eslint max-statements: ["error", 10]*/
/*eslint-env es6*/
function foo() {
var foo1 = 1;
var foo2 = 2;
var foo3 = 3;
var foo4 = 4;
var foo5 = 5;
var foo6 = 6;
var foo7 = 7;
var foo8 = 8;
var foo9 = 9;
var foo10 = 10;
var foo11 = 11; // Too many.
}
let foo = () => {
var foo1 = 1;
var foo2 = 2;
var foo3 = 3;
var foo4 = 4;
var foo5 = 5;
var foo6 = 6;
var foo7 = 7;
var foo8 = 8;
var foo9 = 9;
var foo10 = 10;
var foo11 = 11; // Too many.
};
Examples of correct code for this rule with the default { "max": 10 }
option:
/*eslint max-statements: ["error", 10]*/
/*eslint-env es6*/
function foo() {
var foo1 = 1;
var foo2 = 2;
var foo3 = 3;
var foo4 = 4;
var foo5 = 5;
var foo6 = 6;
var foo7 = 7;
var foo8 = 8;
var foo9 = 9;
var foo10 = 10;
return function () {
// The number of statements in the inner function does not count toward the
// statement maximum.
return 42;
};
}
let foo = () => {
var foo1 = 1;
var foo2 = 2;
var foo3 = 3;
var foo4 = 4;
var foo5 = 5;
var foo6 = 6;
var foo7 = 7;
var foo8 = 8;
var foo9 = 9;
var foo10 = 10;
return function () {
// The number of statements in the inner function does not count toward the
// statement maximum.
return 42;
};
}
ignoreTopLevelFunctions
Examples of additional correct code for this rule with the { "max": 10 }, { "ignoreTopLevelFunctions": true }
options:
/*eslint max-statements: ["error", 10, { "ignoreTopLevelFunctions": true }]*/
function foo() {
var foo1 = 1;
var foo2 = 2;
var foo3 = 3;
var foo4 = 4;
var foo5 = 5;
var foo6 = 6;
var foo7 = 7;
var foo8 = 8;
var foo9 = 9;
var foo10 = 10;
var foo11 = 11;
}
Related Rules
- [complexity](complexity.md)
- [max-depth](max-depth.md)
- [max-len](max-len.md)
- [max-nested-callbacks](max-nested-callbacks.md)
- [max-params](max-params.md) Source: http://eslint.org/docs/rules/
Function has too many statements (66). Maximum allowed is 30. Open
var parseLink = function( editor, element ) {
- Read upRead up
- Exclude checks
enforce a maximum number of statements allowed in function blocks (max-statements)
The max-statements
rule allows you to specify the maximum number of statements allowed in a function.
function foo() {
var bar = 1; // one statement
var baz = 2; // two statements
var qux = 3; // three statements
}
Rule Details
This rule enforces a maximum number of statements allowed in function blocks.
Options
This rule has a number or object option:
-
"max"
(default10
) enforces a maximum number of statements allows in function blocks
Deprecated: The object property maximum
is deprecated; please use the object property max
instead.
This rule has an object option:
-
"ignoreTopLevelFunctions": true
ignores top-level functions
max
Examples of incorrect code for this rule with the default { "max": 10 }
option:
/*eslint max-statements: ["error", 10]*/
/*eslint-env es6*/
function foo() {
var foo1 = 1;
var foo2 = 2;
var foo3 = 3;
var foo4 = 4;
var foo5 = 5;
var foo6 = 6;
var foo7 = 7;
var foo8 = 8;
var foo9 = 9;
var foo10 = 10;
var foo11 = 11; // Too many.
}
let foo = () => {
var foo1 = 1;
var foo2 = 2;
var foo3 = 3;
var foo4 = 4;
var foo5 = 5;
var foo6 = 6;
var foo7 = 7;
var foo8 = 8;
var foo9 = 9;
var foo10 = 10;
var foo11 = 11; // Too many.
};
Examples of correct code for this rule with the default { "max": 10 }
option:
/*eslint max-statements: ["error", 10]*/
/*eslint-env es6*/
function foo() {
var foo1 = 1;
var foo2 = 2;
var foo3 = 3;
var foo4 = 4;
var foo5 = 5;
var foo6 = 6;
var foo7 = 7;
var foo8 = 8;
var foo9 = 9;
var foo10 = 10;
return function () {
// The number of statements in the inner function does not count toward the
// statement maximum.
return 42;
};
}
let foo = () => {
var foo1 = 1;
var foo2 = 2;
var foo3 = 3;
var foo4 = 4;
var foo5 = 5;
var foo6 = 6;
var foo7 = 7;
var foo8 = 8;
var foo9 = 9;
var foo10 = 10;
return function () {
// The number of statements in the inner function does not count toward the
// statement maximum.
return 42;
};
}
ignoreTopLevelFunctions
Examples of additional correct code for this rule with the { "max": 10 }, { "ignoreTopLevelFunctions": true }
options:
/*eslint max-statements: ["error", 10, { "ignoreTopLevelFunctions": true }]*/
function foo() {
var foo1 = 1;
var foo2 = 2;
var foo3 = 3;
var foo4 = 4;
var foo5 = 5;
var foo6 = 6;
var foo7 = 7;
var foo8 = 8;
var foo9 = 9;
var foo10 = 10;
var foo11 = 11;
}
Related Rules
- [complexity](complexity.md)
- [max-depth](max-depth.md)
- [max-len](max-len.md)
- [max-nested-callbacks](max-nested-callbacks.md)
- [max-params](max-params.md) Source: http://eslint.org/docs/rules/
Function onOk
has 130 lines of code (exceeds 25 allowed). Consider refactoring. Open
onOk: function() {
var attributes = {},
removeAttributes = [],
data = {},
me = this,
Function parseLink
has 125 lines of code (exceeds 25 allowed). Consider refactoring. Open
var parseLink = function( editor, element ) {
var href = ( element && ( element.data( 'cke-saved-href' ) || element.getAttribute( 'href' ) ) ) || '',
javascriptMatch, emailMatch, anchorMatch, urlMatch,
retval = {};
Method 'onOk' has a complexity of 32. Open
onOk: function() {
- Read upRead up
- Exclude checks
Limit Cyclomatic Complexity (complexity)
Cyclomatic complexity measures the number of linearly independent paths through a program's source code. This rule allows setting a cyclomatic complexity threshold.
function a(x) {
if (true) {
return x; // 1st path
} else if (false) {
return x+1; // 2nd path
} else {
return 4; // 3rd path
}
}
Rule Details
This rule is aimed at reducing code complexity by capping the amount of cyclomatic complexity allowed in a program. As such, it will warn when the cyclomatic complexity crosses the configured threshold (default is 20
).
Examples of incorrect code for a maximum of 2:
/*eslint complexity: ["error", 2]*/
function a(x) {
if (true) {
return x;
} else if (false) {
return x+1;
} else {
return 4; // 3rd path
}
}
Examples of correct code for a maximum of 2:
/*eslint complexity: ["error", 2]*/
function a(x) {
if (true) {
return x;
} else {
return 4;
}
}
Options
Optionally, you may specify a max
object property:
"complexity": ["error", 2]
is equivalent to
"complexity": ["error", { "max": 2 }]
Deprecated: the object property maximum
is deprecated. Please use the property max
instead.
When Not To Use It
If you can't determine an appropriate complexity limit for your code, then it's best to disable this rule.
Further Reading
Related Rules
- [max-depth](max-depth.md)
- [max-len](max-len.md)
- [max-nested-callbacks](max-nested-callbacks.md)
- [max-params](max-params.md)
- [max-statements](max-statements.md) Source: http://eslint.org/docs/rules/
Function has a complexity of 31. Open
var parseLink = function( editor, element ) {
- Read upRead up
- Exclude checks
Limit Cyclomatic Complexity (complexity)
Cyclomatic complexity measures the number of linearly independent paths through a program's source code. This rule allows setting a cyclomatic complexity threshold.
function a(x) {
if (true) {
return x; // 1st path
} else if (false) {
return x+1; // 2nd path
} else {
return 4; // 3rd path
}
}
Rule Details
This rule is aimed at reducing code complexity by capping the amount of cyclomatic complexity allowed in a program. As such, it will warn when the cyclomatic complexity crosses the configured threshold (default is 20
).
Examples of incorrect code for a maximum of 2:
/*eslint complexity: ["error", 2]*/
function a(x) {
if (true) {
return x;
} else if (false) {
return x+1;
} else {
return 4; // 3rd path
}
}
Examples of correct code for a maximum of 2:
/*eslint complexity: ["error", 2]*/
function a(x) {
if (true) {
return x;
} else {
return 4;
}
}
Options
Optionally, you may specify a max
object property:
"complexity": ["error", 2]
is equivalent to
"complexity": ["error", { "max": 2 }]
Deprecated: the object property maximum
is deprecated. Please use the property max
instead.
When Not To Use It
If you can't determine an appropriate complexity limit for your code, then it's best to disable this rule.
Further Reading
Related Rules
- [max-depth](max-depth.md)
- [max-len](max-len.md)
- [max-nested-callbacks](max-nested-callbacks.md)
- [max-params](max-params.md)
- [max-statements](max-statements.md) Source: http://eslint.org/docs/rules/
Function has a complexity of 8. Open
var linkTypeChanged = function() {
- Read upRead up
- Exclude checks
Limit Cyclomatic Complexity (complexity)
Cyclomatic complexity measures the number of linearly independent paths through a program's source code. This rule allows setting a cyclomatic complexity threshold.
function a(x) {
if (true) {
return x; // 1st path
} else if (false) {
return x+1; // 2nd path
} else {
return 4; // 3rd path
}
}
Rule Details
This rule is aimed at reducing code complexity by capping the amount of cyclomatic complexity allowed in a program. As such, it will warn when the cyclomatic complexity crosses the configured threshold (default is 20
).
Examples of incorrect code for a maximum of 2:
/*eslint complexity: ["error", 2]*/
function a(x) {
if (true) {
return x;
} else if (false) {
return x+1;
} else {
return 4; // 3rd path
}
}
Examples of correct code for a maximum of 2:
/*eslint complexity: ["error", 2]*/
function a(x) {
if (true) {
return x;
} else {
return 4;
}
}
Options
Optionally, you may specify a max
object property:
"complexity": ["error", 2]
is equivalent to
"complexity": ["error", { "max": 2 }]
Deprecated: the object property maximum
is deprecated. Please use the property max
instead.
When Not To Use It
If you can't determine an appropriate complexity limit for your code, then it's best to disable this rule.
Further Reading
Related Rules
- [max-depth](max-depth.md)
- [max-len](max-len.md)
- [max-nested-callbacks](max-nested-callbacks.md)
- [max-params](max-params.md)
- [max-statements](max-statements.md) Source: http://eslint.org/docs/rules/
Function linkTypeChanged
has 26 lines of code (exceeds 25 allowed). Consider refactoring. Open
var linkTypeChanged = function() {
var dialog = this.getDialog(),
partIds = [ 'urlOptions', 'anchorOptions', 'emailOptions' ],
typeValue = this.getValue(),
uploadTab = dialog.definition.getContents( 'upload' ),
Avoid deeply nested control flow statements. Open
if ( ( featureMatch[ 2 ] == 'yes' || featureMatch[ 2 ] == '1' ) && !( featureMatch[ 1 ] in { height:1,width:1,top:1,left:1 } ) )
retval.target[ featureMatch[ 1 ] ] = true;
else if ( isFinite( featureMatch[ 2 ] ) )
retval.target[ featureMatch[ 1 ] ] = featureMatch[ 2 ];
Expected '===' and instead saw '=='. Open
if ( typeValue == 'url' ) {
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected an assignment or function call and instead saw an expression. Open
subjectMatch && ( email.subject = decodeURIComponent( subjectMatch[ 1 ] ) );
- Read upRead up
- Exclude checks
Disallow Unused Expressions (no-unused-expressions)
An unused expression which has no effect on the state of the program indicates a logic error.
For example, n + 1;
is not a syntax error, but it might be a typing mistake where a programmer meant an assignment statement n += 1;
instead.
Rule Details
This rule aims to eliminate unused expressions which have no effect on the state of the program.
This rule does not apply to function calls or constructor calls with the new
operator, because they could have side effects on the state of the program.
var i = 0;
function increment() { i += 1; }
increment(); // return value is unused, but i changed as a side effect
var nThings = 0;
function Thing() { nThings += 1; }
new Thing(); // constructed object is unused, but nThings changed as a side effect
This rule does not apply to directives (which are in the form of literal string expressions such as "use strict";
at the beginning of a script, module, or function).
Sequence expressions (those using a comma, such as a = 1, b = 2
) are always considered unused unless their return value is assigned or used in a condition evaluation, or a function call is made with the sequence expression value.
Options
This rule, in its default state, does not require any arguments. If you would like to enable one or more of the following you may pass an object with the options set as follows:
-
allowShortCircuit
set totrue
will allow you to use short circuit evaluations in your expressions (Default:false
). -
allowTernary
set totrue
will enable you to use ternary operators in your expressions similarly to short circuit evaluations (Default:false
). -
allowTaggedTemplates
set totrue
will enable you to use tagged template literals in your expressions (Default:false
).
These options allow unused expressions only if all of the code paths either directly change the state (for example, assignment statement) or could have side effects (for example, function call).
Examples of incorrect code for the default { "allowShortCircuit": false, "allowTernary": false }
options:
/*eslint no-unused-expressions: "error"*/
0
if(0) 0
{0}
f(0), {}
a && b()
a, b()
c = a, b;
a() && function namedFunctionInExpressionContext () {f();}
(function anIncompleteIIFE () {});
injectGlobal`body{ color: red; }`
Note that one or more string expression statements (with or without semi-colons) will only be considered as unused if they are not in the beginning of a script, module, or function (alone and uninterrupted by other statements). Otherwise, they will be treated as part of a "directive prologue", a section potentially usable by JavaScript engines. This includes "strict mode" directives.
"use strict";
"use asm"
"use stricter";
"use babel"
"any other strings like this in the prologue";
Examples of correct code for the default { "allowShortCircuit": false, "allowTernary": false }
options:
/*eslint no-unused-expressions: "error"*/
{} // In this context, this is a block statement, not an object literal
{myLabel: someVar} // In this context, this is a block statement with a label and expression, not an object literal
function namedFunctionDeclaration () {}
(function aGenuineIIFE () {}());
f()
a = 0
new C
delete a.b
void a
allowShortCircuit
Examples of incorrect code for the { "allowShortCircuit": true }
option:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true }]*/
a || b
Examples of correct code for the { "allowShortCircuit": true }
option:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true }]*/
a && b()
a() || (b = c)
allowTernary
Examples of incorrect code for the { "allowTernary": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTernary": true }]*/
a ? b : 0
a ? b : c()
Examples of correct code for the { "allowTernary": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTernary": true }]*/
a ? b() : c()
a ? (b = c) : d()
allowShortCircuit and allowTernary
Examples of correct code for the { "allowShortCircuit": true, "allowTernary": true }
options:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true, "allowTernary": true }]*/
a ? b() || (c = d) : e()
allowTaggedTemplates
Examples of incorrect code for the { "allowTaggedTemplates": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTaggedTemplates": true }]*/
`some untagged template string`;
Examples of correct code for the { "allowTaggedTemplates": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTaggedTemplates": true }]*/
tag`some tagged template string`;
Source: http://eslint.org/docs/rules/
Expected '===' and instead saw '=='. Open
var text = new CKEDITOR.dom.text( data.type == 'email' ? data.email.address : attributes[ 'data-cke-saved-href' ], editor.document );
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected '===' and instead saw '=='. Open
if ( href == textView || data.type == 'email' && textView.indexOf( '@' ) != -1 ) {
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected '===' and instead saw '=='. Open
element.setHtml( data.type == 'email' ? data.email.address : attributes[ 'data-cke-saved-href' ] );
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected '===' and instead saw '=='. Open
if ( funcName == compiledProtectionFunction.name ) {
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected an assignment or function call and instead saw an expression. Open
bodyMatch && ( email.body = decodeURIComponent( bodyMatch[ 1 ] ) );
- Read upRead up
- Exclude checks
Disallow Unused Expressions (no-unused-expressions)
An unused expression which has no effect on the state of the program indicates a logic error.
For example, n + 1;
is not a syntax error, but it might be a typing mistake where a programmer meant an assignment statement n += 1;
instead.
Rule Details
This rule aims to eliminate unused expressions which have no effect on the state of the program.
This rule does not apply to function calls or constructor calls with the new
operator, because they could have side effects on the state of the program.
var i = 0;
function increment() { i += 1; }
increment(); // return value is unused, but i changed as a side effect
var nThings = 0;
function Thing() { nThings += 1; }
new Thing(); // constructed object is unused, but nThings changed as a side effect
This rule does not apply to directives (which are in the form of literal string expressions such as "use strict";
at the beginning of a script, module, or function).
Sequence expressions (those using a comma, such as a = 1, b = 2
) are always considered unused unless their return value is assigned or used in a condition evaluation, or a function call is made with the sequence expression value.
Options
This rule, in its default state, does not require any arguments. If you would like to enable one or more of the following you may pass an object with the options set as follows:
-
allowShortCircuit
set totrue
will allow you to use short circuit evaluations in your expressions (Default:false
). -
allowTernary
set totrue
will enable you to use ternary operators in your expressions similarly to short circuit evaluations (Default:false
). -
allowTaggedTemplates
set totrue
will enable you to use tagged template literals in your expressions (Default:false
).
These options allow unused expressions only if all of the code paths either directly change the state (for example, assignment statement) or could have side effects (for example, function call).
Examples of incorrect code for the default { "allowShortCircuit": false, "allowTernary": false }
options:
/*eslint no-unused-expressions: "error"*/
0
if(0) 0
{0}
f(0), {}
a && b()
a, b()
c = a, b;
a() && function namedFunctionInExpressionContext () {f();}
(function anIncompleteIIFE () {});
injectGlobal`body{ color: red; }`
Note that one or more string expression statements (with or without semi-colons) will only be considered as unused if they are not in the beginning of a script, module, or function (alone and uninterrupted by other statements). Otherwise, they will be treated as part of a "directive prologue", a section potentially usable by JavaScript engines. This includes "strict mode" directives.
"use strict";
"use asm"
"use stricter";
"use babel"
"any other strings like this in the prologue";
Examples of correct code for the default { "allowShortCircuit": false, "allowTernary": false }
options:
/*eslint no-unused-expressions: "error"*/
{} // In this context, this is a block statement, not an object literal
{myLabel: someVar} // In this context, this is a block statement with a label and expression, not an object literal
function namedFunctionDeclaration () {}
(function aGenuineIIFE () {}());
f()
a = 0
new C
delete a.b
void a
allowShortCircuit
Examples of incorrect code for the { "allowShortCircuit": true }
option:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true }]*/
a || b
Examples of correct code for the { "allowShortCircuit": true }
option:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true }]*/
a && b()
a() || (b = c)
allowTernary
Examples of incorrect code for the { "allowTernary": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTernary": true }]*/
a ? b : 0
a ? b : c()
Examples of correct code for the { "allowTernary": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTernary": true }]*/
a ? b() : c()
a ? (b = c) : d()
allowShortCircuit and allowTernary
Examples of correct code for the { "allowShortCircuit": true, "allowTernary": true }
options:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true, "allowTernary": true }]*/
a ? b() || (c = d) : e()
allowTaggedTemplates
Examples of incorrect code for the { "allowTaggedTemplates": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTaggedTemplates": true }]*/
`some untagged template string`;
Examples of correct code for the { "allowTaggedTemplates": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTaggedTemplates": true }]*/
tag`some tagged template string`;
Source: http://eslint.org/docs/rules/
Expected '===' and instead saw '=='. Open
if ( emailProtection == 'encode' ) {
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected '===' and instead saw '=='. Open
if ( data.target.type == 'popup' ) {
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected '===' and instead saw '=='. Open
if ( ( featureMatch[ 2 ] == 'yes' || featureMatch[ 2 ] == '1' ) && !( featureMatch[ 1 ] in { height:1,width:1,top:1,left:1 } ) )
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected '!==' and instead saw '!='. Open
if ( dialog.getContentElement( 'info', 'linkType' ) && dialog.getValueOf( 'info', 'linkType' ) != 'url' )
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected '===' and instead saw '=='. Open
if ( linkType && linkType.getValue() == 'email' )
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected an assignment or function call and instead saw an expression. Open
body && argList.push( 'body=' + body );
- Read upRead up
- Exclude checks
Disallow Unused Expressions (no-unused-expressions)
An unused expression which has no effect on the state of the program indicates a logic error.
For example, n + 1;
is not a syntax error, but it might be a typing mistake where a programmer meant an assignment statement n += 1;
instead.
Rule Details
This rule aims to eliminate unused expressions which have no effect on the state of the program.
This rule does not apply to function calls or constructor calls with the new
operator, because they could have side effects on the state of the program.
var i = 0;
function increment() { i += 1; }
increment(); // return value is unused, but i changed as a side effect
var nThings = 0;
function Thing() { nThings += 1; }
new Thing(); // constructed object is unused, but nThings changed as a side effect
This rule does not apply to directives (which are in the form of literal string expressions such as "use strict";
at the beginning of a script, module, or function).
Sequence expressions (those using a comma, such as a = 1, b = 2
) are always considered unused unless their return value is assigned or used in a condition evaluation, or a function call is made with the sequence expression value.
Options
This rule, in its default state, does not require any arguments. If you would like to enable one or more of the following you may pass an object with the options set as follows:
-
allowShortCircuit
set totrue
will allow you to use short circuit evaluations in your expressions (Default:false
). -
allowTernary
set totrue
will enable you to use ternary operators in your expressions similarly to short circuit evaluations (Default:false
). -
allowTaggedTemplates
set totrue
will enable you to use tagged template literals in your expressions (Default:false
).
These options allow unused expressions only if all of the code paths either directly change the state (for example, assignment statement) or could have side effects (for example, function call).
Examples of incorrect code for the default { "allowShortCircuit": false, "allowTernary": false }
options:
/*eslint no-unused-expressions: "error"*/
0
if(0) 0
{0}
f(0), {}
a && b()
a, b()
c = a, b;
a() && function namedFunctionInExpressionContext () {f();}
(function anIncompleteIIFE () {});
injectGlobal`body{ color: red; }`
Note that one or more string expression statements (with or without semi-colons) will only be considered as unused if they are not in the beginning of a script, module, or function (alone and uninterrupted by other statements). Otherwise, they will be treated as part of a "directive prologue", a section potentially usable by JavaScript engines. This includes "strict mode" directives.
"use strict";
"use asm"
"use stricter";
"use babel"
"any other strings like this in the prologue";
Examples of correct code for the default { "allowShortCircuit": false, "allowTernary": false }
options:
/*eslint no-unused-expressions: "error"*/
{} // In this context, this is a block statement, not an object literal
{myLabel: someVar} // In this context, this is a block statement with a label and expression, not an object literal
function namedFunctionDeclaration () {}
(function aGenuineIIFE () {}());
f()
a = 0
new C
delete a.b
void a
allowShortCircuit
Examples of incorrect code for the { "allowShortCircuit": true }
option:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true }]*/
a || b
Examples of correct code for the { "allowShortCircuit": true }
option:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true }]*/
a && b()
a() || (b = c)
allowTernary
Examples of incorrect code for the { "allowTernary": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTernary": true }]*/
a ? b : 0
a ? b : c()
Examples of correct code for the { "allowTernary": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTernary": true }]*/
a ? b() : c()
a ? (b = c) : d()
allowShortCircuit and allowTernary
Examples of correct code for the { "allowShortCircuit": true, "allowTernary": true }
options:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true, "allowTernary": true }]*/
a ? b() || (c = d) : e()
allowTaggedTemplates
Examples of incorrect code for the { "allowTaggedTemplates": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTaggedTemplates": true }]*/
`some untagged template string`;
Examples of correct code for the { "allowTaggedTemplates": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTaggedTemplates": true }]*/
tag`some tagged template string`;
Source: http://eslint.org/docs/rules/
Expected '===' and instead saw '=='. Open
if ( href == textView || data.type == 'email' && textView.indexOf( '@' ) != -1 ) {
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected '!==' and instead saw '!='. Open
if ( emailProtection && emailProtection != 'encode' ) {
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Unexpected alert. Open
alert( commonLang.invalidValue );
- Read upRead up
- Exclude checks
Disallow Use of Alert (no-alert)
JavaScript's alert
, confirm
, and prompt
functions are widely considered to be obtrusive as UI elements and should be replaced by a more appropriate custom UI implementation. Furthermore, alert
is often used while debugging code, which should be removed before deployment to production.
alert("here!");
Rule Details
This rule is aimed at catching debugging code that should be removed and popup UI elements that should be replaced with less obtrusive, custom UIs. As such, it will warn when it encounters alert
, prompt
, and confirm
function calls which are not shadowed.
Examples of incorrect code for this rule:
/*eslint no-alert: "error"*/
alert("here!");
confirm("Are you sure?");
prompt("What's your name?", "John Doe");
Examples of correct code for this rule:
/*eslint no-alert: "error"*/
customAlert("Something happened!");
customConfirm("Are you sure?");
customPrompt("Who are you?");
function foo() {
var alert = myCustomLib.customAlert;
alert();
}
Related Rules
- [no-console](no-console.md)
- [no-debugger](no-debugger.md) Source: http://eslint.org/docs/rules/
Expected '===' and instead saw '=='. Open
if ( partIds[ i ] == typeValue + 'Options' )
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected an assignment or function call and instead saw an expression. Open
i > 0 && retval.push( ',' );
- Read upRead up
- Exclude checks
Disallow Unused Expressions (no-unused-expressions)
An unused expression which has no effect on the state of the program indicates a logic error.
For example, n + 1;
is not a syntax error, but it might be a typing mistake where a programmer meant an assignment statement n += 1;
instead.
Rule Details
This rule aims to eliminate unused expressions which have no effect on the state of the program.
This rule does not apply to function calls or constructor calls with the new
operator, because they could have side effects on the state of the program.
var i = 0;
function increment() { i += 1; }
increment(); // return value is unused, but i changed as a side effect
var nThings = 0;
function Thing() { nThings += 1; }
new Thing(); // constructed object is unused, but nThings changed as a side effect
This rule does not apply to directives (which are in the form of literal string expressions such as "use strict";
at the beginning of a script, module, or function).
Sequence expressions (those using a comma, such as a = 1, b = 2
) are always considered unused unless their return value is assigned or used in a condition evaluation, or a function call is made with the sequence expression value.
Options
This rule, in its default state, does not require any arguments. If you would like to enable one or more of the following you may pass an object with the options set as follows:
-
allowShortCircuit
set totrue
will allow you to use short circuit evaluations in your expressions (Default:false
). -
allowTernary
set totrue
will enable you to use ternary operators in your expressions similarly to short circuit evaluations (Default:false
). -
allowTaggedTemplates
set totrue
will enable you to use tagged template literals in your expressions (Default:false
).
These options allow unused expressions only if all of the code paths either directly change the state (for example, assignment statement) or could have side effects (for example, function call).
Examples of incorrect code for the default { "allowShortCircuit": false, "allowTernary": false }
options:
/*eslint no-unused-expressions: "error"*/
0
if(0) 0
{0}
f(0), {}
a && b()
a, b()
c = a, b;
a() && function namedFunctionInExpressionContext () {f();}
(function anIncompleteIIFE () {});
injectGlobal`body{ color: red; }`
Note that one or more string expression statements (with or without semi-colons) will only be considered as unused if they are not in the beginning of a script, module, or function (alone and uninterrupted by other statements). Otherwise, they will be treated as part of a "directive prologue", a section potentially usable by JavaScript engines. This includes "strict mode" directives.
"use strict";
"use asm"
"use stricter";
"use babel"
"any other strings like this in the prologue";
Examples of correct code for the default { "allowShortCircuit": false, "allowTernary": false }
options:
/*eslint no-unused-expressions: "error"*/
{} // In this context, this is a block statement, not an object literal
{myLabel: someVar} // In this context, this is a block statement with a label and expression, not an object literal
function namedFunctionDeclaration () {}
(function aGenuineIIFE () {}());
f()
a = 0
new C
delete a.b
void a
allowShortCircuit
Examples of incorrect code for the { "allowShortCircuit": true }
option:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true }]*/
a || b
Examples of correct code for the { "allowShortCircuit": true }
option:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true }]*/
a && b()
a() || (b = c)
allowTernary
Examples of incorrect code for the { "allowTernary": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTernary": true }]*/
a ? b : 0
a ? b : c()
Examples of correct code for the { "allowTernary": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTernary": true }]*/
a ? b() : c()
a ? (b = c) : d()
allowShortCircuit and allowTernary
Examples of correct code for the { "allowShortCircuit": true, "allowTernary": true }
options:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true, "allowTernary": true }]*/
a ? b() || (c = d) : e()
allowTaggedTemplates
Examples of incorrect code for the { "allowTaggedTemplates": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTaggedTemplates": true }]*/
`some untagged template string`;
Examples of correct code for the { "allowTaggedTemplates": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTaggedTemplates": true }]*/
tag`some tagged template string`;
Source: http://eslint.org/docs/rules/
Expected an assignment or function call and instead saw an expression. Open
argList && linkHref.push( '+\'', escapeSingleQuote( argList ), '\'' );
- Read upRead up
- Exclude checks
Disallow Unused Expressions (no-unused-expressions)
An unused expression which has no effect on the state of the program indicates a logic error.
For example, n + 1;
is not a syntax error, but it might be a typing mistake where a programmer meant an assignment statement n += 1;
instead.
Rule Details
This rule aims to eliminate unused expressions which have no effect on the state of the program.
This rule does not apply to function calls or constructor calls with the new
operator, because they could have side effects on the state of the program.
var i = 0;
function increment() { i += 1; }
increment(); // return value is unused, but i changed as a side effect
var nThings = 0;
function Thing() { nThings += 1; }
new Thing(); // constructed object is unused, but nThings changed as a side effect
This rule does not apply to directives (which are in the form of literal string expressions such as "use strict";
at the beginning of a script, module, or function).
Sequence expressions (those using a comma, such as a = 1, b = 2
) are always considered unused unless their return value is assigned or used in a condition evaluation, or a function call is made with the sequence expression value.
Options
This rule, in its default state, does not require any arguments. If you would like to enable one or more of the following you may pass an object with the options set as follows:
-
allowShortCircuit
set totrue
will allow you to use short circuit evaluations in your expressions (Default:false
). -
allowTernary
set totrue
will enable you to use ternary operators in your expressions similarly to short circuit evaluations (Default:false
). -
allowTaggedTemplates
set totrue
will enable you to use tagged template literals in your expressions (Default:false
).
These options allow unused expressions only if all of the code paths either directly change the state (for example, assignment statement) or could have side effects (for example, function call).
Examples of incorrect code for the default { "allowShortCircuit": false, "allowTernary": false }
options:
/*eslint no-unused-expressions: "error"*/
0
if(0) 0
{0}
f(0), {}
a && b()
a, b()
c = a, b;
a() && function namedFunctionInExpressionContext () {f();}
(function anIncompleteIIFE () {});
injectGlobal`body{ color: red; }`
Note that one or more string expression statements (with or without semi-colons) will only be considered as unused if they are not in the beginning of a script, module, or function (alone and uninterrupted by other statements). Otherwise, they will be treated as part of a "directive prologue", a section potentially usable by JavaScript engines. This includes "strict mode" directives.
"use strict";
"use asm"
"use stricter";
"use babel"
"any other strings like this in the prologue";
Examples of correct code for the default { "allowShortCircuit": false, "allowTernary": false }
options:
/*eslint no-unused-expressions: "error"*/
{} // In this context, this is a block statement, not an object literal
{myLabel: someVar} // In this context, this is a block statement with a label and expression, not an object literal
function namedFunctionDeclaration () {}
(function aGenuineIIFE () {}());
f()
a = 0
new C
delete a.b
void a
allowShortCircuit
Examples of incorrect code for the { "allowShortCircuit": true }
option:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true }]*/
a || b
Examples of correct code for the { "allowShortCircuit": true }
option:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true }]*/
a && b()
a() || (b = c)
allowTernary
Examples of incorrect code for the { "allowTernary": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTernary": true }]*/
a ? b : 0
a ? b : c()
Examples of correct code for the { "allowTernary": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTernary": true }]*/
a ? b() : c()
a ? (b = c) : d()
allowShortCircuit and allowTernary
Examples of correct code for the { "allowShortCircuit": true, "allowTernary": true }
options:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true, "allowTernary": true }]*/
a ? b() || (c = d) : e()
allowTaggedTemplates
Examples of incorrect code for the { "allowTaggedTemplates": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTaggedTemplates": true }]*/
`some untagged template string`;
Examples of correct code for the { "allowTaggedTemplates": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTaggedTemplates": true }]*/
tag`some tagged template string`;
Source: http://eslint.org/docs/rules/
Expected '===' and instead saw '=='. Open
if ( emailProtection == 'encode' ) {
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected '!==' and instead saw '!='. Open
if ( !dialog.getContentElement( 'info', 'linkType' ) || dialog.getValueOf( 'info', 'linkType' ) != 'email' )
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected '!==' and instead saw '!='. Open
var protocol = ( data.url && data.url.protocol != undefined ) ? data.url.protocol : 'http://',
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected '!==' and instead saw '!='. Open
if ( href == textView || data.type == 'email' && textView.indexOf( '@' ) != -1 ) {
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected '===' and instead saw '=='. Open
if ( linkType && linkType.getValue() == 'url' ) {
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected '!==' and instead saw '!='. Open
if ( data.target.type != 'notSet' && data.target.name )
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected an assignment or function call and instead saw an expression. Open
subject && argList.push( 'subject=' + subject );
- Read upRead up
- Exclude checks
Disallow Unused Expressions (no-unused-expressions)
An unused expression which has no effect on the state of the program indicates a logic error.
For example, n + 1;
is not a syntax error, but it might be a typing mistake where a programmer meant an assignment statement n += 1;
instead.
Rule Details
This rule aims to eliminate unused expressions which have no effect on the state of the program.
This rule does not apply to function calls or constructor calls with the new
operator, because they could have side effects on the state of the program.
var i = 0;
function increment() { i += 1; }
increment(); // return value is unused, but i changed as a side effect
var nThings = 0;
function Thing() { nThings += 1; }
new Thing(); // constructed object is unused, but nThings changed as a side effect
This rule does not apply to directives (which are in the form of literal string expressions such as "use strict";
at the beginning of a script, module, or function).
Sequence expressions (those using a comma, such as a = 1, b = 2
) are always considered unused unless their return value is assigned or used in a condition evaluation, or a function call is made with the sequence expression value.
Options
This rule, in its default state, does not require any arguments. If you would like to enable one or more of the following you may pass an object with the options set as follows:
-
allowShortCircuit
set totrue
will allow you to use short circuit evaluations in your expressions (Default:false
). -
allowTernary
set totrue
will enable you to use ternary operators in your expressions similarly to short circuit evaluations (Default:false
). -
allowTaggedTemplates
set totrue
will enable you to use tagged template literals in your expressions (Default:false
).
These options allow unused expressions only if all of the code paths either directly change the state (for example, assignment statement) or could have side effects (for example, function call).
Examples of incorrect code for the default { "allowShortCircuit": false, "allowTernary": false }
options:
/*eslint no-unused-expressions: "error"*/
0
if(0) 0
{0}
f(0), {}
a && b()
a, b()
c = a, b;
a() && function namedFunctionInExpressionContext () {f();}
(function anIncompleteIIFE () {});
injectGlobal`body{ color: red; }`
Note that one or more string expression statements (with or without semi-colons) will only be considered as unused if they are not in the beginning of a script, module, or function (alone and uninterrupted by other statements). Otherwise, they will be treated as part of a "directive prologue", a section potentially usable by JavaScript engines. This includes "strict mode" directives.
"use strict";
"use asm"
"use stricter";
"use babel"
"any other strings like this in the prologue";
Examples of correct code for the default { "allowShortCircuit": false, "allowTernary": false }
options:
/*eslint no-unused-expressions: "error"*/
{} // In this context, this is a block statement, not an object literal
{myLabel: someVar} // In this context, this is a block statement with a label and expression, not an object literal
function namedFunctionDeclaration () {}
(function aGenuineIIFE () {}());
f()
a = 0
new C
delete a.b
void a
allowShortCircuit
Examples of incorrect code for the { "allowShortCircuit": true }
option:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true }]*/
a || b
Examples of correct code for the { "allowShortCircuit": true }
option:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true }]*/
a && b()
a() || (b = c)
allowTernary
Examples of incorrect code for the { "allowTernary": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTernary": true }]*/
a ? b : 0
a ? b : c()
Examples of correct code for the { "allowTernary": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTernary": true }]*/
a ? b() : c()
a ? (b = c) : d()
allowShortCircuit and allowTernary
Examples of correct code for the { "allowShortCircuit": true, "allowTernary": true }
options:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true, "allowTernary": true }]*/
a ? b() || (c = d) : e()
allowTaggedTemplates
Examples of incorrect code for the { "allowTaggedTemplates": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTaggedTemplates": true }]*/
`some untagged template string`;
Examples of correct code for the { "allowTaggedTemplates": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTaggedTemplates": true }]*/
tag`some tagged template string`;
Source: http://eslint.org/docs/rules/
Expected an assignment or function call and instead saw an expression. Open
CKEDITOR.plugins.link.synAnchorSelector ? retval.adv.advCSSClasses = getLinkClass( element ) : advAttr( 'advCSSClasses', 'class' );
- Read upRead up
- Exclude checks
Disallow Unused Expressions (no-unused-expressions)
An unused expression which has no effect on the state of the program indicates a logic error.
For example, n + 1;
is not a syntax error, but it might be a typing mistake where a programmer meant an assignment statement n += 1;
instead.
Rule Details
This rule aims to eliminate unused expressions which have no effect on the state of the program.
This rule does not apply to function calls or constructor calls with the new
operator, because they could have side effects on the state of the program.
var i = 0;
function increment() { i += 1; }
increment(); // return value is unused, but i changed as a side effect
var nThings = 0;
function Thing() { nThings += 1; }
new Thing(); // constructed object is unused, but nThings changed as a side effect
This rule does not apply to directives (which are in the form of literal string expressions such as "use strict";
at the beginning of a script, module, or function).
Sequence expressions (those using a comma, such as a = 1, b = 2
) are always considered unused unless their return value is assigned or used in a condition evaluation, or a function call is made with the sequence expression value.
Options
This rule, in its default state, does not require any arguments. If you would like to enable one or more of the following you may pass an object with the options set as follows:
-
allowShortCircuit
set totrue
will allow you to use short circuit evaluations in your expressions (Default:false
). -
allowTernary
set totrue
will enable you to use ternary operators in your expressions similarly to short circuit evaluations (Default:false
). -
allowTaggedTemplates
set totrue
will enable you to use tagged template literals in your expressions (Default:false
).
These options allow unused expressions only if all of the code paths either directly change the state (for example, assignment statement) or could have side effects (for example, function call).
Examples of incorrect code for the default { "allowShortCircuit": false, "allowTernary": false }
options:
/*eslint no-unused-expressions: "error"*/
0
if(0) 0
{0}
f(0), {}
a && b()
a, b()
c = a, b;
a() && function namedFunctionInExpressionContext () {f();}
(function anIncompleteIIFE () {});
injectGlobal`body{ color: red; }`
Note that one or more string expression statements (with or without semi-colons) will only be considered as unused if they are not in the beginning of a script, module, or function (alone and uninterrupted by other statements). Otherwise, they will be treated as part of a "directive prologue", a section potentially usable by JavaScript engines. This includes "strict mode" directives.
"use strict";
"use asm"
"use stricter";
"use babel"
"any other strings like this in the prologue";
Examples of correct code for the default { "allowShortCircuit": false, "allowTernary": false }
options:
/*eslint no-unused-expressions: "error"*/
{} // In this context, this is a block statement, not an object literal
{myLabel: someVar} // In this context, this is a block statement with a label and expression, not an object literal
function namedFunctionDeclaration () {}
(function aGenuineIIFE () {}());
f()
a = 0
new C
delete a.b
void a
allowShortCircuit
Examples of incorrect code for the { "allowShortCircuit": true }
option:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true }]*/
a || b
Examples of correct code for the { "allowShortCircuit": true }
option:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true }]*/
a && b()
a() || (b = c)
allowTernary
Examples of incorrect code for the { "allowTernary": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTernary": true }]*/
a ? b : 0
a ? b : c()
Examples of correct code for the { "allowTernary": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTernary": true }]*/
a ? b() : c()
a ? (b = c) : d()
allowShortCircuit and allowTernary
Examples of correct code for the { "allowShortCircuit": true, "allowTernary": true }
options:
/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true, "allowTernary": true }]*/
a ? b() || (c = d) : e()
allowTaggedTemplates
Examples of incorrect code for the { "allowTaggedTemplates": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTaggedTemplates": true }]*/
`some untagged template string`;
Examples of correct code for the { "allowTaggedTemplates": true }
option:
/*eslint no-unused-expressions: ["error", { "allowTaggedTemplates": true }]*/
tag`some tagged template string`;
Source: http://eslint.org/docs/rules/
Expected '===' and instead saw '=='. Open
if ( ( featureMatch[ 2 ] == 'yes' || featureMatch[ 2 ] == '1' ) && !( featureMatch[ 1 ] in { height:1,width:1,top:1,left:1 } ) )
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected '===' and instead saw '=='. Open
if ( linkType && linkType.getValue() == 'email' )
- Read upRead up
- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
BUG found Open
// IE BUG: target attribute is an empty string instead of null in IE if it's not set.
- Exclude checks
Similar blocks of code found in 4 locations. Consider refactoring. Open
{
type: 'hbox',
children: [
{
type: 'checkbox',
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 75.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 4 locations. Consider refactoring. Open
{
type: 'hbox',
children: [
{
type: 'checkbox',
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 75.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 4 locations. Consider refactoring. Open
{
type: 'hbox',
children: [
{
type: 'checkbox',
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 75.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 4 locations. Consider refactoring. Open
{
type: 'hbox',
children: [
{
type: 'checkbox',
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 75.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 2 locations. Consider refactoring. Open
for ( var i = 0; i < data.anchors.length; i++ ) {
if ( data.anchors[ i ].id )
this.add( data.anchors[ i ].id );
}
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 70.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 2 locations. Consider refactoring. Open
for ( var i = 0; i < data.anchors.length; i++ ) {
if ( data.anchors[ i ].name )
this.add( data.anchors[ i ].name );
}
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 70.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 3 locations. Consider refactoring. Open
setup: function( data ) {
if ( data.anchors.length > 0 )
this.getElement().show();
else
this.getElement().hide();
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 62.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 3 locations. Consider refactoring. Open
setup: function( data ) {
if ( data.anchors.length > 0 )
this.getElement().show();
else
this.getElement().hide();
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 62.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 3 locations. Consider refactoring. Open
setup: function( data ) {
if ( data.anchors.length < 1 )
this.getElement().show();
else
this.getElement().hide();
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 62.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 7 locations. Consider refactoring. Open
commit: function( data ) {
if ( !data.anchor )
data.anchor = {};
data.anchor.id = this.getValue();
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 55.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 7 locations. Consider refactoring. Open
commit: function( data ) {
if ( !data.url )
data.url = {};
data.url.protocol = this.getValue();
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 55.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 7 locations. Consider refactoring. Open
commit: function( data ) {
if ( !data.anchor )
data.anchor = {};
data.anchor.name = this.getValue();
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 55.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 7 locations. Consider refactoring. Open
commit: function( data ) {
if ( !data.email )
data.email = {};
data.email.address = this.getValue();
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 55.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 7 locations. Consider refactoring. Open
commit: function( data ) {
if ( !data.email )
data.email = {};
data.email.subject = this.getValue();
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 55.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 7 locations. Consider refactoring. Open
commit: function( data ) {
if ( !data.target )
data.target = {};
data.target.type = this.getValue();
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 55.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 7 locations. Consider refactoring. Open
commit: function( data ) {
if ( !data.email )
data.email = {};
data.email.body = this.getValue();
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 55.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 3 locations. Consider refactoring. Open
setup: function( data ) {
if ( !this.getDialog().getContentElement( 'info', 'linkType' ) )
this.getElement().show();
}
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 50.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 3 locations. Consider refactoring. Open
setup: function( data ) {
if ( !this.getDialog().getContentElement( 'info', 'linkType' ) )
this.getElement().hide();
}
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 50.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 3 locations. Consider refactoring. Open
setup: function( data ) {
if ( !this.getDialog().getContentElement( 'info', 'linkType' ) )
this.getElement().hide();
}
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 50.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76