eval can be harmful. Open
field.onpaste = eval("(function () { " + field.getAttribute("onpaste") + " })");
- Read upRead up
- Exclude checks
Disallow eval() (no-eval)
JavaScript's eval()
function is potentially dangerous and is often misused. Using eval()
on untrusted code can open a program up to several different injection attacks. The use of eval()
in most contexts can be substituted for a better, alternative approach to a problem.
var obj = { x: "foo" },
key = "x",
value = eval("obj." + key);
Rule Details
This rule is aimed at preventing potentially dangerous, unnecessary, and slow code by disallowing the use of the eval()
function. As such, it will warn whenever the eval()
function is used.
Examples of incorrect code for this rule:
/*eslint no-eval: "error"*/
var obj = { x: "foo" },
key = "x",
value = eval("obj." + key);
(0, eval)("var a = 0");
var foo = eval;
foo("var a = 0");
// This `this` is the global object.
this.eval("var a = 0");
Example of additional incorrect code for this rule when browser
environment is set to true
:
/*eslint no-eval: "error"*/
/*eslint-env browser*/
window.eval("var a = 0");
Example of additional incorrect code for this rule when node
environment is set to true
:
/*eslint no-eval: "error"*/
/*eslint-env node*/
global.eval("var a = 0");
Examples of correct code for this rule:
/*eslint no-eval: "error"*/
/*eslint-env es6*/
var obj = { x: "foo" },
key = "x",
value = obj[key];
class A {
foo() {
// This is a user-defined method.
this.eval("var a = 0");
}
eval() {
}
}
Options
This rule has an option to allow indirect calls to eval
.
Indirect calls to eval
are less dangerous than direct calls to eval
because they cannot dynamically change the scope. Because of this, they also will not negatively impact performance to the degree of direct eval
.
{
"no-eval": ["error", {"allowIndirect": true}] // default is false
}
Example of incorrect code for this rule with the {"allowIndirect": true}
option:
/*eslint no-eval: "error"*/
var obj = { x: "foo" },
key = "x",
value = eval("obj." + key);
Examples of correct code for this rule with the {"allowIndirect": true}
option:
/*eslint no-eval: "error"*/
(0, eval)("var a = 0");
var foo = eval;
foo("var a = 0");
this.eval("var a = 0");
/*eslint no-eval: "error"*/
/*eslint-env browser*/
window.eval("var a = 0");
/*eslint no-eval: "error"*/
/*eslint-env node*/
global.eval("var a = 0");
Known Limitations
- This rule is warning every
eval()
even if theeval
is not global's. This behavior is in order to detect calls of directeval
. Such as:
module.exports = function(eval) {
// If the value of this `eval` is built-in `eval` function, this is a
// call of direct `eval`.
eval("var a = 0");
};
- This rule cannot catch renaming the global object. Such as:
var foo = window;
foo.eval("var a = 0");
Further Reading
Related Rules
- [no-implied-eval](no-implied-eval.md) Source: http://eslint.org/docs/rules/
Implied eval. Consider passing a function instead of a string. Open
checkStatusInt = setTimeout('calcStat();', 250);
- Read upRead up
- Exclude checks
Disallow Implied eval() (no-implied-eval)
It's considered a good practice to avoid using eval()
in JavaScript. There are security and performance implications involved with doing so, which is why many linters (including ESLint) recommend disallowing eval()
. However, there are some other ways to pass a string and have it interpreted as JavaScript code that have similar concerns.
The first is using setTimeout()
, setInterval()
or execScript()
(Internet Explorer only), both of which can accept a string of JavaScript code as their first argument. For example:
setTimeout("alert('Hi!');", 100);
This is considered an implied eval()
because a string of JavaScript code is
passed in to be interpreted. The same can be done with setInterval()
and execScript()
. Both interpret the JavaScript code in the global scope. For both setTimeout()
and setInterval()
, the first argument can also be a function, and that is considered safer and is more performant:
setTimeout(function() {
alert("Hi!");
}, 100);
The best practice is to always use a function for the first argument of setTimeout()
and setInterval()
(and avoid execScript()
).
Rule Details
This rule aims to eliminate implied eval()
through the use of setTimeout()
, setInterval()
or execScript()
. As such, it will warn when either function is used with a string as the first argument.
Examples of incorrect code for this rule:
/*eslint no-implied-eval: "error"*/
setTimeout("alert('Hi!');", 100);
setInterval("alert('Hi!');", 100);
execScript("alert('Hi!')");
window.setTimeout("count = 5", 10);
window.setInterval("foo = bar", 10);
Examples of correct code for this rule:
/*eslint no-implied-eval: "error"*/
setTimeout(function() {
alert("Hi!");
}, 100);
setInterval(function() {
alert("Hi!");
}, 100);
When Not To Use It
If you want to allow setTimeout()
and setInterval()
with string arguments, then you can safely disable this rule.
Related Rules
- [no-eval](no-eval.md) Source: http://eslint.org/docs/rules/
Function stopCP
has a Cognitive Complexity of 35 (exceeds 5 allowed). Consider refactoring. Open
(function stopCP () {
var onload = window.onload;
window.onload = function () {
if (typeof onload == "function") {
- Read upRead up
Cognitive Complexity
Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.
A method's cognitive complexity is based on a few simple rules:
- Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
- Code is considered more complex for each "break in the linear flow of the code"
- Code is considered more complex when "flow breaking structures are nested"
Further reading
Function 'endTest' has too many statements (45). Maximum allowed is 30. Open
function endTest() {
- 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 'calcStat' has too many statements (34). Maximum allowed is 30. Open
function calcStat() {
- 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 a complexity of 9. Open
window.onload = 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 endTest
has 50 lines of code (exceeds 25 allowed). Consider refactoring. Open
function endTest() {
//Clear the timer that tracks the progress of the test, since it's complete
clearTimeout(checkStatusInt);
//Initialize an object with the current date/time so we can calculate the difference
Function 'calcStat' has a complexity of 8. Open
function calcStat() {
- 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 calcStat
has 44 lines of code (exceeds 25 allowed). Consider refactoring. Open
function calcStat() {
//If something goes wrong, we don't want to cancel the test -- so fallback error proection (in a way, just standard error handling)
try {
//Reset the timer to fire the statistical update function again in 250ms
//We do this here so that if the test has ended (below) we can cancel and stop it
Function stopCP
has 42 lines of code (exceeds 25 allowed). Consider refactoring. Open
(function stopCP () {
var onload = window.onload;
window.onload = function () {
if (typeof onload == "function") {
Function onload
has 39 lines of code (exceeds 25 allowed). Consider refactoring. Open
window.onload = function () {
if (typeof onload == "function") {
onload.apply(this, arguments);
}
Consider simplifying this complex logical expression. Open
if (
person.search("ota") === - 1 &&
person.search("Ota") === - 1 &&
person.search("fruhwirth") === - 1 &&
person.search("Fruhwirth") === - 1 &&
Function calcStat
has a Cognitive Complexity of 11 (exceeds 5 allowed). Consider refactoring. Open
function calcStat() {
//If something goes wrong, we don't want to cancel the test -- so fallback error proection (in a way, just standard error handling)
try {
//Reset the timer to fire the statistical update function again in 250ms
//We do this here so that if the test has ended (below) we can cancel and stop it
- Read upRead up
Cognitive Complexity
Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.
A method's cognitive complexity is based on a few simple rules:
- Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
- Code is considered more complex for each "break in the linear flow of the code"
- Code is considered more complex when "flow breaking structures are nested"
Further reading
Function myFunction
has 28 lines of code (exceeds 25 allowed). Consider refactoring. Open
function myFunction()
{
var person = prompt("Please enter your name", "");
// Profanity Filter (if there is a better way to do this LMK)
if (
Function endTest
has a Cognitive Complexity of 8 (exceeds 5 allowed). Consider refactoring. Open
function endTest() {
//Clear the timer that tracks the progress of the test, since it's complete
clearTimeout(checkStatusInt);
//Initialize an object with the current date/time so we can calculate the difference
- Read upRead up
Cognitive Complexity
Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.
A method's cognitive complexity is based on a few simple rules:
- Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
- Code is considered more complex for each "break in the linear flow of the code"
- Code is considered more complex when "flow breaking structures are nested"
Further reading
Function readTextFile
has a Cognitive Complexity of 6 (exceeds 5 allowed). Consider refactoring. Open
function readTextFile(file, arrayData)
{
var rawFile = new XMLHttpRequest();
rawFile.open("GET", file, false);
rawFile.onreadystatechange = function ()
- Read upRead up
Cognitive Complexity
Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.
A method's cognitive complexity is based on a few simple rules:
- Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
- Code is considered more complex for each "break in the linear flow of the code"
- Code is considered more complex when "flow breaking structures are nested"
Further reading
Expected '===' and instead saw '=='. Open
if(rawFile.status == 200 || rawFile.status == 0)
- 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 (typeof onload == "function") {
- 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/
Spaces are hard to count. Use {2}. Open
wpmType = Math.round(((document.JobOp.typed.value.replace(/ /g, " ").split(" ").length) / totalTime) * 60)
- Read upRead up
- Exclude checks
disallow multiple spaces in regular expression literals (no-regex-spaces)
Regular expressions can be very complex and difficult to understand, which is why it's important to keep them as simple as possible in order to avoid mistakes. One of the more error-prone things you can do with a regular expression is to use more than one space, such as:
var re = /foo bar/;
In this regular expression, it's very hard to tell how many spaces are intended to be matched. It's better to use only one space and then specify how many spaces are expected, such as:
var re = /foo {3}bar/;
Now it is very clear that three spaces are expected to be matched.
Rule Details
This rule disallows multiple spaces in regular expression literals.
Examples of incorrect code for this rule:
/*eslint no-regex-spaces: "error"*/
var re = /foo bar/;
var re = new RegExp("foo bar");
Examples of correct code for this rule:
/*eslint no-regex-spaces: "error"*/
var re = /foo {3}bar/;
var re = new RegExp("foo {3}bar");
When Not To Use It
If you want to allow multiple spaces in a regular expression, then you can safely turn this rule off.
Related Rules
- [no-div-regex](no-div-regex.md)
- [no-control-regex](no-control-regex.md) Source: http://eslint.org/docs/rules/
Spaces are hard to count. Use {2}. Open
var thisTyped = document.JobOp.typed.value.replace(/ /g, " ");
- Read upRead up
- Exclude checks
disallow multiple spaces in regular expression literals (no-regex-spaces)
Regular expressions can be very complex and difficult to understand, which is why it's important to keep them as simple as possible in order to avoid mistakes. One of the more error-prone things you can do with a regular expression is to use more than one space, such as:
var re = /foo bar/;
In this regular expression, it's very hard to tell how many spaces are intended to be matched. It's better to use only one space and then specify how many spaces are expected, such as:
var re = /foo {3}bar/;
Now it is very clear that three spaces are expected to be matched.
Rule Details
This rule disallows multiple spaces in regular expression literals.
Examples of incorrect code for this rule:
/*eslint no-regex-spaces: "error"*/
var re = /foo bar/;
var re = new RegExp("foo bar");
Examples of correct code for this rule:
/*eslint no-regex-spaces: "error"*/
var re = /foo {3}bar/;
var re = new RegExp("foo {3}bar");
When Not To Use It
If you want to allow multiple spaces in a regular expression, then you can safely turn this rule off.
Related Rules
- [no-div-regex](no-div-regex.md)
- [no-control-regex](no-control-regex.md) Source: http://eslint.org/docs/rules/
'i' is already defined. Open
for (var i = 0; i < textareas.length; i++) {
- Read upRead up
- Exclude checks
disallow variable redeclaration (no-redeclare)
In JavaScript, it's possible to redeclare the same variable name using var
. This can lead to confusion as to where the variable is actually declared and initialized.
Rule Details
This rule is aimed at eliminating variables that have multiple declarations in the same scope.
Examples of incorrect code for this rule:
/*eslint no-redeclare: "error"*/
var a = 3;
var a = 10;
Examples of correct code for this rule:
/*eslint no-redeclare: "error"*/
var a = 3;
// ...
a = 10;
Options
This rule takes one optional argument, an object with a boolean property "builtinGlobals"
. It defaults to false
.
If set to true
, this rule also checks redeclaration of built-in globals, such as Object
, Array
, Number
...
builtinGlobals
Examples of incorrect code for the { "builtinGlobals": true }
option:
/*eslint no-redeclare: ["error", { "builtinGlobals": true }]*/
var Object = 0;
Examples of incorrect code for the { "builtinGlobals": true }
option and the browser
environment:
/*eslint no-redeclare: ["error", { "builtinGlobals": true }]*/
/*eslint-env browser*/
var top = 0;
The browser
environment has many built-in global variables (for example, top
). Some of built-in global variables cannot be redeclared.
Source: http://eslint.org/docs/rules/
Unexpected alert. Open
alert(msg);
- 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 (typeof this.previousValue == "undefined") {
- 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/
Spaces are hard to count. Use {2}. Open
aftReport = "<b>Typing Summary:</b><br>You typed " + (document.JobOp.typed.value.replace(/ /g, " ").split(" ").length) + " words in " + totalTime + " seconds, a speed of about " + wpmType + " words per minute.\n\nYou also had " + badWords + " errors, and " + goodWords + " correct words, giving scoring of " + ((goodWords / (goodWords + badWords)) * 100).toFixed(2) + "%.<br><br>" + aftReport;
- Read upRead up
- Exclude checks
disallow multiple spaces in regular expression literals (no-regex-spaces)
Regular expressions can be very complex and difficult to understand, which is why it's important to keep them as simple as possible in order to avoid mistakes. One of the more error-prone things you can do with a regular expression is to use more than one space, such as:
var re = /foo bar/;
In this regular expression, it's very hard to tell how many spaces are intended to be matched. It's better to use only one space and then specify how many spaces are expected, such as:
var re = /foo {3}bar/;
Now it is very clear that three spaces are expected to be matched.
Rule Details
This rule disallows multiple spaces in regular expression literals.
Examples of incorrect code for this rule:
/*eslint no-regex-spaces: "error"*/
var re = /foo bar/;
var re = new RegExp("foo bar");
Examples of correct code for this rule:
/*eslint no-regex-spaces: "error"*/
var re = /foo {3}bar/;
var re = new RegExp("foo {3}bar");
When Not To Use It
If you want to allow multiple spaces in a regular expression, then you can safely turn this rule off.
Related Rules
- [no-div-regex](no-div-regex.md)
- [no-control-regex](no-control-regex.md) Source: http://eslint.org/docs/rules/
Unexpected alert. Open
alert(person);
- 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/
Unexpected alert. Open
alert("Invalid option");
- 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/
Don't make functions within a loop. Open
field.oninput = function () {
- Read upRead up
- Exclude checks
Disallow Functions in Loops (no-loop-func)
Writing functions within loops tends to result in errors due to the way the function creates a closure around the loop. For example:
for (var i = 0; i < 10; i++) {
funcs[i] = function() {
return i;
};
}
In this case, you would expect each function created within the loop to return a different number. In reality, each function returns 10, because that was the last value of i
in the scope.
let
or const
mitigate this problem.
/*eslint-env es6*/
for (let i = 0; i < 10; i++) {
funcs[i] = function() {
return i;
};
}
In this case, each function created within the loop returns a different number as expected.
Rule Details
This error is raised to highlight a piece of code that may not work as you expect it to and could also indicate a misunderstanding of how the language works. Your code may run without any problems if you do not fix this error, but in some situations it could behave unexpectedly.
Examples of incorrect code for this rule:
/*eslint no-loop-func: "error"*/
/*eslint-env es6*/
for (var i=10; i; i--) {
(function() { return i; })();
}
while(i) {
var a = function() { return i; };
a();
}
do {
function a() { return i; };
a();
} while (i);
let foo = 0;
for (let i=10; i; i--) {
// Bad, function is referencing block scoped variable in the outer scope.
var a = function() { return foo; };
a();
}
Examples of correct code for this rule:
/*eslint no-loop-func: "error"*/
/*eslint-env es6*/
var a = function() {};
for (var i=10; i; i--) {
a();
}
for (var i=10; i; i--) {
var a = function() {}; // OK, no references to variables in the outer scopes.
a();
}
for (let i=10; i; i--) {
var a = function() { return i; }; // OK, all references are referring to block scoped variables in the loop.
a();
}
var foo = 100;
for (let i=10; i; i--) {
var a = function() { return foo; }; // OK, all references are referring to never modified variables.
a();
}
//... no modifications of foo after this loop ...
Source: http://eslint.org/docs/rules/
Spaces are hard to count. Use {2}. Open
var neededValues = Left(document.JobOp.given.value, typedValues.length).replace(/ /g, " ").split(" ");
- Read upRead up
- Exclude checks
disallow multiple spaces in regular expression literals (no-regex-spaces)
Regular expressions can be very complex and difficult to understand, which is why it's important to keep them as simple as possible in order to avoid mistakes. One of the more error-prone things you can do with a regular expression is to use more than one space, such as:
var re = /foo bar/;
In this regular expression, it's very hard to tell how many spaces are intended to be matched. It's better to use only one space and then specify how many spaces are expected, such as:
var re = /foo {3}bar/;
Now it is very clear that three spaces are expected to be matched.
Rule Details
This rule disallows multiple spaces in regular expression literals.
Examples of incorrect code for this rule:
/*eslint no-regex-spaces: "error"*/
var re = /foo bar/;
var re = new RegExp("foo bar");
Examples of correct code for this rule:
/*eslint no-regex-spaces: "error"*/
var re = /foo {3}bar/;
var re = new RegExp("foo {3}bar");
When Not To Use It
If you want to allow multiple spaces in a regular expression, then you can safely turn this rule off.
Related Rules
- [no-div-regex](no-div-regex.md)
- [no-control-regex](no-control-regex.md) Source: http://eslint.org/docs/rules/
Spaces are hard to count. Use {2}. Open
var typedValues = document.JobOp.typed.value.replace(/ /g, " ");
- Read upRead up
- Exclude checks
disallow multiple spaces in regular expression literals (no-regex-spaces)
Regular expressions can be very complex and difficult to understand, which is why it's important to keep them as simple as possible in order to avoid mistakes. One of the more error-prone things you can do with a regular expression is to use more than one space, such as:
var re = /foo bar/;
In this regular expression, it's very hard to tell how many spaces are intended to be matched. It's better to use only one space and then specify how many spaces are expected, such as:
var re = /foo {3}bar/;
Now it is very clear that three spaces are expected to be matched.
Rule Details
This rule disallows multiple spaces in regular expression literals.
Examples of incorrect code for this rule:
/*eslint no-regex-spaces: "error"*/
var re = /foo bar/;
var re = new RegExp("foo bar");
Examples of correct code for this rule:
/*eslint no-regex-spaces: "error"*/
var re = /foo {3}bar/;
var re = new RegExp("foo {3}bar");
When Not To Use It
If you want to allow multiple spaces in a regular expression, then you can safely turn this rule off.
Related Rules
- [no-div-regex](no-div-regex.md)
- [no-control-regex](no-control-regex.md) Source: http://eslint.org/docs/rules/
Empty block statement. Open
} catch (e) {}
- Read upRead up
- Exclude checks
disallow empty block statements (no-empty)
Empty block statements, while not technically errors, usually occur due to refactoring that wasn't completed. They can cause confusion when reading code.
Rule Details
This rule disallows empty block statements. This rule ignores block statements which contain a comment (for example, in an empty catch
or finally
block of a try
statement to indicate that execution should continue regardless of errors).
Examples of incorrect code for this rule:
/*eslint no-empty: "error"*/
if (foo) {
}
while (foo) {
}
switch(foo) {
}
try {
doSomething();
} catch(ex) {
} finally {
}
Examples of correct code for this rule:
/*eslint no-empty: "error"*/
if (foo) {
// empty
}
while (foo) {
/* empty */
}
try {
doSomething();
} catch (ex) {
// continue regardless of error
}
try {
doSomething();
} finally {
/* continue regardless of error */
}
Options
This rule has an object option for exceptions:
-
"allowEmptyCatch": true
allows emptycatch
clauses (that is, which do not contain a comment)
allowEmptyCatch
Examples of additional correct code for this rule with the { "allowEmptyCatch": true }
option:
/* eslint no-empty: ["error", { "allowEmptyCatch": true }] */
try {
doSomething();
} catch (ex) {}
try {
doSomething();
}
catch (ex) {}
finally {
/* continue regardless of error */
}
When Not To Use It
If you intentionally use empty block statements then you can disable this rule.
Related Rules
- [no-empty-function](./no-empty-function.md) Source: http://eslint.org/docs/rules/
'i' is already defined. Open
for (var i = 0; i < fields.length; i++) {
- Read upRead up
- Exclude checks
disallow variable redeclaration (no-redeclare)
In JavaScript, it's possible to redeclare the same variable name using var
. This can lead to confusion as to where the variable is actually declared and initialized.
Rule Details
This rule is aimed at eliminating variables that have multiple declarations in the same scope.
Examples of incorrect code for this rule:
/*eslint no-redeclare: "error"*/
var a = 3;
var a = 10;
Examples of correct code for this rule:
/*eslint no-redeclare: "error"*/
var a = 3;
// ...
a = 10;
Options
This rule takes one optional argument, an object with a boolean property "builtinGlobals"
. It defaults to false
.
If set to true
, this rule also checks redeclaration of built-in globals, such as Object
, Array
, Number
...
builtinGlobals
Examples of incorrect code for the { "builtinGlobals": true }
option:
/*eslint no-redeclare: ["error", { "builtinGlobals": true }]*/
var Object = 0;
Examples of incorrect code for the { "builtinGlobals": true }
option and the browser
environment:
/*eslint no-redeclare: ["error", { "builtinGlobals": true }]*/
/*eslint-env browser*/
var top = 0;
The browser
environment has many built-in global variables (for example, top
). Some of built-in global variables cannot be redeclared.
Source: http://eslint.org/docs/rules/
'i' is already defined. Open
for (var i = 0; i < word; i++) {
- Read upRead up
- Exclude checks
disallow variable redeclaration (no-redeclare)
In JavaScript, it's possible to redeclare the same variable name using var
. This can lead to confusion as to where the variable is actually declared and initialized.
Rule Details
This rule is aimed at eliminating variables that have multiple declarations in the same scope.
Examples of incorrect code for this rule:
/*eslint no-redeclare: "error"*/
var a = 3;
var a = 10;
Examples of correct code for this rule:
/*eslint no-redeclare: "error"*/
var a = 3;
// ...
a = 10;
Options
This rule takes one optional argument, an object with a boolean property "builtinGlobals"
. It defaults to false
.
If set to true
, this rule also checks redeclaration of built-in globals, such as Object
, Array
, Number
...
builtinGlobals
Examples of incorrect code for the { "builtinGlobals": true }
option:
/*eslint no-redeclare: ["error", { "builtinGlobals": true }]*/
var Object = 0;
Examples of incorrect code for the { "builtinGlobals": true }
option and the browser
environment:
/*eslint no-redeclare: ["error", { "builtinGlobals": true }]*/
/*eslint-env browser*/
var top = 0;
The browser
environment has many built-in global variables (for example, top
). Some of built-in global variables cannot be redeclared.
Source: http://eslint.org/docs/rules/
Unexpected prompt. Open
var person = prompt("Please enter your name", "");
- 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(rawFile.status == 200 || rawFile.status == 0)
- 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/
Move the invocation into the parens that contain the function. Open
(function stopCP () {
- Read upRead up
- Exclude checks
Require IIFEs to be Wrapped (wrap-iife)
You can immediately invoke function expressions, but not function declarations. A common technique to create an immediately-invoked function expression (IIFE) is to wrap a function declaration in parentheses. The opening parentheses causes the contained function to be parsed as an expression, rather than a declaration.
// function expression could be unwrapped
var x = function () { return { y: 1 };}();
// function declaration must be wrapped
function () { /* side effects */ }(); // SyntaxError
Rule Details
This rule requires all immediately-invoked function expressions to be wrapped in parentheses.
Options
This rule has two options, a string option and an object option.
String option:
-
"outside"
enforces always wrapping the call expression. The default is"outside"
. -
"inside"
enforces always wrapping the function expression. -
"any"
enforces always wrapping, but allows either style.
Object option:
-
"functionPrototypeMethods": true
additionally enforces wrapping function expressions invoked using.call
and.apply
. The default isfalse
.
outside
Examples of incorrect code for the default "outside"
option:
/*eslint wrap-iife: ["error", "outside"]*/
var x = function () { return { y: 1 };}(); // unwrapped
var x = (function () { return { y: 1 };})(); // wrapped function expression
Examples of correct code for the default "outside"
option:
/*eslint wrap-iife: ["error", "outside"]*/
var x = (function () { return { y: 1 };}()); // wrapped call expression
inside
Examples of incorrect code for the "inside"
option:
/*eslint wrap-iife: ["error", "inside"]*/
var x = function () { return { y: 1 };}(); // unwrapped
var x = (function () { return { y: 1 };}()); // wrapped call expression
Examples of correct code for the "inside"
option:
/*eslint wrap-iife: ["error", "inside"]*/
var x = (function () { return { y: 1 };})(); // wrapped function expression
any
Examples of incorrect code for the "any"
option:
/*eslint wrap-iife: ["error", "any"]*/
var x = function () { return { y: 1 };}(); // unwrapped
Examples of correct code for the "any"
option:
/*eslint wrap-iife: ["error", "any"]*/
var x = (function () { return { y: 1 };}()); // wrapped call expression
var x = (function () { return { y: 1 };})(); // wrapped function expression
functionPrototypeMethods
Examples of incorrect code for this rule with the "inside", { "functionPrototypeMethods": true }
options:
/* eslint wrap-iife: [2, "inside", { functionPrototypeMethods: true }] */
var x = function(){ foo(); }()
var x = (function(){ foo(); }())
var x = function(){ foo(); }.call(bar)
var x = (function(){ foo(); }.call(bar))
Examples of correct code for this rule with the "inside", { "functionPrototypeMethods": true }
options:
/* eslint wrap-iife: [2, "inside", { functionPrototypeMethods: true }] */
var x = (function(){ foo(); })()
var x = (function(){ foo(); }).call(bar)
Source: http://eslint.org/docs/rules/
Similar blocks of code found in 2 locations. Consider refactoring. Open
if (Number(3600 - totalTime) < 5) {
tTT.innerHTML = "<font color=\"Red\">" + String(totalTime.toFixed(2)) + " sec. / " + String(Number(3600 - totalTime).toFixed(2)) + " sec.</font>";
} else {
if (Number(3600 - totalTime) < 15) {
tTT.innerHTML = "<font color=\"Orange\">" + String(totalTime.toFixed(2)) + " sec. / " + String(Number(3600 - totalTime).toFixed(2)) + " sec.</font>";
- 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 63.
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
if (Number(3600 - totalTime) < 15) {
tTT.innerHTML = "<font color=\"Orange\">" + String(totalTime.toFixed(2)) + " sec. / " + String(Number(3600 - totalTime).toFixed(2)) + " sec.</font>";
} else {
tTT.innerHTML = String(totalTime.toFixed(2)) + " sec. / " + String(Number(3600 - totalTime).toFixed(2)) + " sec.";
}
- 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 63.
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