Showing 1,297 of 1,297 total issues
Expected 'undefined' and instead saw 'void'. Open
dirpath = void 0, sakuraname = void 0;
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Disallow use of the void operator. (no-void)
The void
operator takes an operand and returns undefined
: void expression
will evaluate expression
and return undefined
. It can be used to ignore any side effects expression
may produce:
The common case of using void
operator is to get a "pure" undefined
value as prior to ES5 the undefined
variable was mutable:
// will always return undefined
(function(){
return void 0;
})();
// will return 1 in ES3 and undefined in ES5+
(function(){
undefined = 1;
return undefined;
})();
// will throw TypeError in ES5+
(function(){
'use strict';
undefined = 1;
})();
Another common case is to minify code as void 0
is shorter than undefined
:
foo = void 0;
foo = undefined;
When used with IIFE (immediately-invoked function expression), void
can be used to force the function keyword to be treated as an expression instead of a declaration:
var foo = 1;
void function(){ foo = 1; }() // will assign foo a value of 1
+function(){ foo = 1; }() // same as above
function(){ foo = 1; }() // will throw SyntaxError
Some code styles prohibit void
operator, marking it as non-obvious and hard to read.
Rule Details
This rule aims to eliminate use of void operator.
Examples of incorrect code for this rule:
/*eslint no-void: "error"*/
void foo
var foo = void bar();
When Not To Use It
If you intentionally use the void
operator then you can disable this rule.
Further Reading
Related Rules
- [no-undef-init](no-undef-init.md)
- [no-undefined](no-undefined.md) Source: http://eslint.org/docs/rules/
No magic number: 0. Open
ghost_result = void 0, balloon_result = void 0;
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Disallow Magic Numbers (no-magic-numbers)
'Magic numbers' are numbers that occur multiple time in code without an explicit meaning. They should preferably be replaced by named constants.
var now = Date.now(),
inOneHour = now + (60 * 60 * 1000);
Rule Details
The no-magic-numbers
rule aims to make code more readable and refactoring easier by ensuring that special numbers
are declared as constants to make their meaning explicit.
Examples of incorrect code for this rule:
/*eslint no-magic-numbers: "error"*/
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * 0.25);
/*eslint no-magic-numbers: "error"*/
var data = ['foo', 'bar', 'baz'];
var dataLast = data[2];
/*eslint no-magic-numbers: "error"*/
var SECONDS;
SECONDS = 60;
Examples of correct code for this rule:
/*eslint no-magic-numbers: "error"*/
var TAX = 0.25;
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * TAX);
Options
ignore
An array of numbers to ignore. It's set to []
by default.
If provided, it must be an Array
.
Examples of correct code for the sample { "ignore": [1] }
option:
/*eslint no-magic-numbers: ["error", { "ignore": [1] }]*/
var data = ['foo', 'bar', 'baz'];
var dataLast = data.length && data[data.length - 1];
ignoreArrayIndexes
A boolean to specify if numbers used as array indexes are considered okay. false
by default.
Examples of correct code for the { "ignoreArrayIndexes": true }
option:
/*eslint no-magic-numbers: ["error", { "ignoreArrayIndexes": true }]*/
var data = ['foo', 'bar', 'baz'];
var dataLast = data[2];
enforceConst
A boolean to specify if we should check for the const keyword in variable declaration of numbers. false
by default.
Examples of incorrect code for the { "enforceConst": true }
option:
/*eslint no-magic-numbers: ["error", { "enforceConst": true }]*/
var TAX = 0.25;
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * TAX);
detectObjects
A boolean to specify if we should detect numbers when setting object properties for example. false
by default.
Examples of incorrect code for the { "detectObjects": true }
option:
/*eslint no-magic-numbers: ["error", { "detectObjects": true }]*/
var magic = {
tax: 0.25
};
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * magic.tax);
Examples of correct code for the { "detectObjects": true }
option:
/*eslint no-magic-numbers: ["error", { "detectObjects": true }]*/
var TAX = 0.25;
var magic = {
tax: TAX
};
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * magic.tax);
Source: http://eslint.org/docs/rules/
Missing trailing comma. Open
}
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require or disallow trailing commas (comma-dangle)
Trailing commas in object literals are valid according to the ECMAScript 5 (and ECMAScript 3!) spec. However, IE8 (when not in IE8 document mode) and below will throw an error when it encounters trailing commas in JavaScript.
var foo = {
bar: "baz",
qux: "quux",
};
Trailing commas simplify adding and removing items to objects and arrays, since only the lines you are modifying must be touched. Another argument in favor of trailing commas is that it improves the clarity of diffs when an item is added or removed from an object or array:
Less clear:
var foo = {
- bar: "baz",
- qux: "quux"
+ bar: "baz"
};
More clear:
var foo = {
bar: "baz",
- qux: "quux",
};
Rule Details
This rule enforces consistent use of trailing commas in object and array literals.
Options
This rule has a string option or an object option:
{
"comma-dangle": ["error", "never"],
// or
"comma-dangle": ["error", {
"arrays": "never",
"objects": "never",
"imports": "never",
"exports": "never",
"functions": "ignore",
}]
}
-
"never"
(default) disallows trailing commas -
"always"
requires trailing commas -
"always-multiline"
requires trailing commas when the last element or property is in a different line than the closing]
or}
and disallows trailing commas when the last element or property is on the same line as the closing]
or}
-
"only-multiline"
allows (but does not require) trailing commas when the last element or property is in a different line than the closing]
or}
and disallows trailing commas when the last element or property is on the same line as the closing]
or}
Trailing commas in function declarations and function calls are valid syntax since ECMAScript 2017; however, the string option does not check these situations for backwards compatibility.
You can also use an object option to configure this rule for each type of syntax.
Each of the following options can be set to "never"
, "always"
, "always-multiline"
, "only-multiline"
, or "ignore"
.
The default for each option is "never"
unless otherwise specified.
-
arrays
is for array literals and array patterns of destructuring. (e.g.let [a,] = [1,];
) -
objects
is for object literals and object patterns of destructuring. (e.g.let {a,} = {a: 1};
) -
imports
is for import declarations of ES Modules. (e.g.import {a,} from "foo";
) -
exports
is for export declarations of ES Modules. (e.g.export {a,};
) -
functions
is for function declarations and function calls. (e.g.(function(a,){ })(b,);
)
functions
is set to"ignore"
by default for consistency with the string option.
never
Examples of incorrect code for this rule with the default "never"
option:
/*eslint comma-dangle: ["error", "never"]*/
var foo = {
bar: "baz",
qux: "quux",
};
var arr = [1,2,];
foo({
bar: "baz",
qux: "quux",
});
Examples of correct code for this rule with the default "never"
option:
/*eslint comma-dangle: ["error", "never"]*/
var foo = {
bar: "baz",
qux: "quux"
};
var arr = [1,2];
foo({
bar: "baz",
qux: "quux"
});
always
Examples of incorrect code for this rule with the "always"
option:
/*eslint comma-dangle: ["error", "always"]*/
var foo = {
bar: "baz",
qux: "quux"
};
var arr = [1,2];
foo({
bar: "baz",
qux: "quux"
});
Examples of correct code for this rule with the "always"
option:
/*eslint comma-dangle: ["error", "always"]*/
var foo = {
bar: "baz",
qux: "quux",
};
var arr = [1,2,];
foo({
bar: "baz",
qux: "quux",
});
always-multiline
Examples of incorrect code for this rule with the "always-multiline"
option:
/*eslint comma-dangle: ["error", "always-multiline"]*/
var foo = {
bar: "baz",
qux: "quux"
};
var foo = { bar: "baz", qux: "quux", };
var arr = [1,2,];
var arr = [1,
2,];
var arr = [
1,
2
];
foo({
bar: "baz",
qux: "quux"
});
Examples of correct code for this rule with the "always-multiline"
option:
/*eslint comma-dangle: ["error", "always-multiline"]*/
var foo = {
bar: "baz",
qux: "quux",
};
var foo = {bar: "baz", qux: "quux"};
var arr = [1,2];
var arr = [1,
2];
var arr = [
1,
2,
];
foo({
bar: "baz",
qux: "quux",
});
only-multiline
Examples of incorrect code for this rule with the "only-multiline"
option:
/*eslint comma-dangle: ["error", "only-multiline"]*/
var foo = { bar: "baz", qux: "quux", };
var arr = [1,2,];
var arr = [1,
2,];
Examples of correct code for this rule with the "only-multiline"
option:
/*eslint comma-dangle: ["error", "only-multiline"]*/
var foo = {
bar: "baz",
qux: "quux",
};
var foo = {
bar: "baz",
qux: "quux"
};
var foo = {bar: "baz", qux: "quux"};
var arr = [1,2];
var arr = [1,
2];
var arr = [
1,
2,
];
var arr = [
1,
2
];
foo({
bar: "baz",
qux: "quux",
});
foo({
bar: "baz",
qux: "quux"
});
functions
Examples of incorrect code for this rule with the {"functions": "never"}
option:
/*eslint comma-dangle: ["error", {"functions": "never"}]*/
function foo(a, b,) {
}
foo(a, b,);
new foo(a, b,);
Examples of correct code for this rule with the {"functions": "never"}
option:
/*eslint comma-dangle: ["error", {"functions": "never"}]*/
function foo(a, b) {
}
foo(a, b);
new foo(a, b);
Examples of incorrect code for this rule with the {"functions": "always"}
option:
/*eslint comma-dangle: ["error", {"functions": "always"}]*/
function foo(a, b) {
}
foo(a, b);
new foo(a, b);
Examples of correct code for this rule with the {"functions": "always"}
option:
/*eslint comma-dangle: ["error", {"functions": "always"}]*/
function foo(a, b,) {
}
foo(a, b,);
new foo(a, b,);
When Not To Use It
You can turn this rule off if you are not concerned with dangling commas. Source: http://eslint.org/docs/rules/
Unexpected var, use let or const instead. Open
var _keys2 = _interopRequireDefault(_keys);
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require let
or const
instead of var
(no-var)
ECMAScript 6 allows programmers to create variables with block scope instead of function scope using the let
and const
keywords. Block scope is common in many other programming languages and helps programmers avoid mistakes
such as:
var count = people.length;
var enoughFood = count > sandwiches.length;
if (enoughFood) {
var count = sandwiches.length; // accidentally overriding the count variable
console.log("We have " + count + " sandwiches for everyone. Plenty for all!");
}
// our count variable is no longer accurate
console.log("We have " + count + " people and " + sandwiches.length + " sandwiches!");
Rule Details
This rule is aimed at discouraging the use of var
and encouraging the use of const
or let
instead.
Examples
Examples of incorrect code for this rule:
/*eslint no-var: "error"*/
var x = "y";
var CONFIG = {};
Examples of correct code for this rule:
/*eslint no-var: "error"*/
/*eslint-env es6*/
let x = "y";
const CONFIG = {};
When Not To Use It
In addition to non-ES6 environments, existing JavaScript projects that are beginning to introduce ES6 into their
codebase may not want to apply this rule if the cost of migrating from var
to let
is too costly.
Source: http://eslint.org/docs/rules/
Missing trailing comma. Open
}
- Read upRead up
- Exclude checks
require or disallow trailing commas (comma-dangle)
Trailing commas in object literals are valid according to the ECMAScript 5 (and ECMAScript 3!) spec. However, IE8 (when not in IE8 document mode) and below will throw an error when it encounters trailing commas in JavaScript.
var foo = {
bar: "baz",
qux: "quux",
};
Trailing commas simplify adding and removing items to objects and arrays, since only the lines you are modifying must be touched. Another argument in favor of trailing commas is that it improves the clarity of diffs when an item is added or removed from an object or array:
Less clear:
var foo = {
- bar: "baz",
- qux: "quux"
+ bar: "baz"
};
More clear:
var foo = {
bar: "baz",
- qux: "quux",
};
Rule Details
This rule enforces consistent use of trailing commas in object and array literals.
Options
This rule has a string option or an object option:
{
"comma-dangle": ["error", "never"],
// or
"comma-dangle": ["error", {
"arrays": "never",
"objects": "never",
"imports": "never",
"exports": "never",
"functions": "ignore",
}]
}
-
"never"
(default) disallows trailing commas -
"always"
requires trailing commas -
"always-multiline"
requires trailing commas when the last element or property is in a different line than the closing]
or}
and disallows trailing commas when the last element or property is on the same line as the closing]
or}
-
"only-multiline"
allows (but does not require) trailing commas when the last element or property is in a different line than the closing]
or}
and disallows trailing commas when the last element or property is on the same line as the closing]
or}
Trailing commas in function declarations and function calls are valid syntax since ECMAScript 2017; however, the string option does not check these situations for backwards compatibility.
You can also use an object option to configure this rule for each type of syntax.
Each of the following options can be set to "never"
, "always"
, "always-multiline"
, "only-multiline"
, or "ignore"
.
The default for each option is "never"
unless otherwise specified.
-
arrays
is for array literals and array patterns of destructuring. (e.g.let [a,] = [1,];
) -
objects
is for object literals and object patterns of destructuring. (e.g.let {a,} = {a: 1};
) -
imports
is for import declarations of ES Modules. (e.g.import {a,} from "foo";
) -
exports
is for export declarations of ES Modules. (e.g.export {a,};
) -
functions
is for function declarations and function calls. (e.g.(function(a,){ })(b,);
)
functions
is set to"ignore"
by default for consistency with the string option.
never
Examples of incorrect code for this rule with the default "never"
option:
/*eslint comma-dangle: ["error", "never"]*/
var foo = {
bar: "baz",
qux: "quux",
};
var arr = [1,2,];
foo({
bar: "baz",
qux: "quux",
});
Examples of correct code for this rule with the default "never"
option:
/*eslint comma-dangle: ["error", "never"]*/
var foo = {
bar: "baz",
qux: "quux"
};
var arr = [1,2];
foo({
bar: "baz",
qux: "quux"
});
always
Examples of incorrect code for this rule with the "always"
option:
/*eslint comma-dangle: ["error", "always"]*/
var foo = {
bar: "baz",
qux: "quux"
};
var arr = [1,2];
foo({
bar: "baz",
qux: "quux"
});
Examples of correct code for this rule with the "always"
option:
/*eslint comma-dangle: ["error", "always"]*/
var foo = {
bar: "baz",
qux: "quux",
};
var arr = [1,2,];
foo({
bar: "baz",
qux: "quux",
});
always-multiline
Examples of incorrect code for this rule with the "always-multiline"
option:
/*eslint comma-dangle: ["error", "always-multiline"]*/
var foo = {
bar: "baz",
qux: "quux"
};
var foo = { bar: "baz", qux: "quux", };
var arr = [1,2,];
var arr = [1,
2,];
var arr = [
1,
2
];
foo({
bar: "baz",
qux: "quux"
});
Examples of correct code for this rule with the "always-multiline"
option:
/*eslint comma-dangle: ["error", "always-multiline"]*/
var foo = {
bar: "baz",
qux: "quux",
};
var foo = {bar: "baz", qux: "quux"};
var arr = [1,2];
var arr = [1,
2];
var arr = [
1,
2,
];
foo({
bar: "baz",
qux: "quux",
});
only-multiline
Examples of incorrect code for this rule with the "only-multiline"
option:
/*eslint comma-dangle: ["error", "only-multiline"]*/
var foo = { bar: "baz", qux: "quux", };
var arr = [1,2,];
var arr = [1,
2,];
Examples of correct code for this rule with the "only-multiline"
option:
/*eslint comma-dangle: ["error", "only-multiline"]*/
var foo = {
bar: "baz",
qux: "quux",
};
var foo = {
bar: "baz",
qux: "quux"
};
var foo = {bar: "baz", qux: "quux"};
var arr = [1,2];
var arr = [1,
2];
var arr = [
1,
2,
];
var arr = [
1,
2
];
foo({
bar: "baz",
qux: "quux",
});
foo({
bar: "baz",
qux: "quux"
});
functions
Examples of incorrect code for this rule with the {"functions": "never"}
option:
/*eslint comma-dangle: ["error", {"functions": "never"}]*/
function foo(a, b,) {
}
foo(a, b,);
new foo(a, b,);
Examples of correct code for this rule with the {"functions": "never"}
option:
/*eslint comma-dangle: ["error", {"functions": "never"}]*/
function foo(a, b) {
}
foo(a, b);
new foo(a, b);
Examples of incorrect code for this rule with the {"functions": "always"}
option:
/*eslint comma-dangle: ["error", {"functions": "always"}]*/
function foo(a, b) {
}
foo(a, b);
new foo(a, b);
Examples of correct code for this rule with the {"functions": "always"}
option:
/*eslint comma-dangle: ["error", {"functions": "always"}]*/
function foo(a, b,) {
}
foo(a, b,);
new foo(a, b,);
When Not To Use It
You can turn this rule off if you are not concerned with dangling commas. Source: http://eslint.org/docs/rules/
Expected a default case. Open
switch (_context11.prev = _context11.next) {
- Read upRead up
- Exclude checks
Require Default Case in Switch Statements (default-case)
Some code conventions require that all switch
statements have a default
case, even if the default case is empty, such as:
switch (foo) {
case 1:
doSomething();
break;
case 2:
doSomething();
break;
default:
// do nothing
}
The thinking is that it's better to always explicitly state what the default behavior should be so that it's clear whether or not the developer forgot to include the default behavior by mistake.
Other code conventions allow you to skip the default
case so long as there is a comment indicating the omission is intentional, such as:
switch (foo) {
case 1:
doSomething();
break;
case 2:
doSomething();
break;
// no default
}
Once again, the intent here is to show that the developer intended for there to be no default behavior.
Rule Details
This rule aims to require default
case in switch
statements. You may optionally include a // no default
after the last case
if there is no default
case. The comment may be in any desired case, such as // No Default
.
Examples of incorrect code for this rule:
/*eslint default-case: "error"*/
switch (a) {
case 1:
/* code */
break;
}
Examples of correct code for this rule:
/*eslint default-case: "error"*/
switch (a) {
case 1:
/* code */
break;
default:
/* code */
break;
}
switch (a) {
case 1:
/* code */
break;
// no default
}
switch (a) {
case 1:
/* code */
break;
// No Default
}
Options
This rule accepts a single options argument:
- Set the
commentPattern
option to a regular expression string to change the default/^no default$/i
comment test pattern
commentPattern
Examples of correct code for the { "commentPattern": "^skip\\sdefault" }
option:
/*eslint default-case: ["error", { "commentPattern": "^skip\\sdefault" }]*/
switch(a) {
case 1:
/* code */
break;
// skip default
}
switch(a) {
case 1:
/* code */
break;
// skip default case
}
When Not To Use It
If you don't want to enforce a default
case for switch
statements, you can safely disable this rule.
Related Rules
- [no-fallthrough](no-fallthrough.md) Source: http://eslint.org/docs/rules/
No magic number: 13. Open
case 13:
- Read upRead up
- Exclude checks
Disallow Magic Numbers (no-magic-numbers)
'Magic numbers' are numbers that occur multiple time in code without an explicit meaning. They should preferably be replaced by named constants.
var now = Date.now(),
inOneHour = now + (60 * 60 * 1000);
Rule Details
The no-magic-numbers
rule aims to make code more readable and refactoring easier by ensuring that special numbers
are declared as constants to make their meaning explicit.
Examples of incorrect code for this rule:
/*eslint no-magic-numbers: "error"*/
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * 0.25);
/*eslint no-magic-numbers: "error"*/
var data = ['foo', 'bar', 'baz'];
var dataLast = data[2];
/*eslint no-magic-numbers: "error"*/
var SECONDS;
SECONDS = 60;
Examples of correct code for this rule:
/*eslint no-magic-numbers: "error"*/
var TAX = 0.25;
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * TAX);
Options
ignore
An array of numbers to ignore. It's set to []
by default.
If provided, it must be an Array
.
Examples of correct code for the sample { "ignore": [1] }
option:
/*eslint no-magic-numbers: ["error", { "ignore": [1] }]*/
var data = ['foo', 'bar', 'baz'];
var dataLast = data.length && data[data.length - 1];
ignoreArrayIndexes
A boolean to specify if numbers used as array indexes are considered okay. false
by default.
Examples of correct code for the { "ignoreArrayIndexes": true }
option:
/*eslint no-magic-numbers: ["error", { "ignoreArrayIndexes": true }]*/
var data = ['foo', 'bar', 'baz'];
var dataLast = data[2];
enforceConst
A boolean to specify if we should check for the const keyword in variable declaration of numbers. false
by default.
Examples of incorrect code for the { "enforceConst": true }
option:
/*eslint no-magic-numbers: ["error", { "enforceConst": true }]*/
var TAX = 0.25;
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * TAX);
detectObjects
A boolean to specify if we should detect numbers when setting object properties for example. false
by default.
Examples of incorrect code for the { "detectObjects": true }
option:
/*eslint no-magic-numbers: ["error", { "detectObjects": true }]*/
var magic = {
tax: 0.25
};
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * magic.tax);
Examples of correct code for the { "detectObjects": true }
option:
/*eslint no-magic-numbers: ["error", { "detectObjects": true }]*/
var TAX = 0.25;
var magic = {
tax: TAX
};
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * magic.tax);
Source: http://eslint.org/docs/rules/
No magic number: 39. Open
}, _callee11, this, [[3, 39]]);
- Read upRead up
- Exclude checks
Disallow Magic Numbers (no-magic-numbers)
'Magic numbers' are numbers that occur multiple time in code without an explicit meaning. They should preferably be replaced by named constants.
var now = Date.now(),
inOneHour = now + (60 * 60 * 1000);
Rule Details
The no-magic-numbers
rule aims to make code more readable and refactoring easier by ensuring that special numbers
are declared as constants to make their meaning explicit.
Examples of incorrect code for this rule:
/*eslint no-magic-numbers: "error"*/
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * 0.25);
/*eslint no-magic-numbers: "error"*/
var data = ['foo', 'bar', 'baz'];
var dataLast = data[2];
/*eslint no-magic-numbers: "error"*/
var SECONDS;
SECONDS = 60;
Examples of correct code for this rule:
/*eslint no-magic-numbers: "error"*/
var TAX = 0.25;
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * TAX);
Options
ignore
An array of numbers to ignore. It's set to []
by default.
If provided, it must be an Array
.
Examples of correct code for the sample { "ignore": [1] }
option:
/*eslint no-magic-numbers: ["error", { "ignore": [1] }]*/
var data = ['foo', 'bar', 'baz'];
var dataLast = data.length && data[data.length - 1];
ignoreArrayIndexes
A boolean to specify if numbers used as array indexes are considered okay. false
by default.
Examples of correct code for the { "ignoreArrayIndexes": true }
option:
/*eslint no-magic-numbers: ["error", { "ignoreArrayIndexes": true }]*/
var data = ['foo', 'bar', 'baz'];
var dataLast = data[2];
enforceConst
A boolean to specify if we should check for the const keyword in variable declaration of numbers. false
by default.
Examples of incorrect code for the { "enforceConst": true }
option:
/*eslint no-magic-numbers: ["error", { "enforceConst": true }]*/
var TAX = 0.25;
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * TAX);
detectObjects
A boolean to specify if we should detect numbers when setting object properties for example. false
by default.
Examples of incorrect code for the { "detectObjects": true }
option:
/*eslint no-magic-numbers: ["error", { "detectObjects": true }]*/
var magic = {
tax: 0.25
};
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * magic.tax);
Examples of correct code for the { "detectObjects": true }
option:
/*eslint no-magic-numbers: ["error", { "detectObjects": true }]*/
var TAX = 0.25;
var magic = {
tax: TAX
};
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * magic.tax);
Source: http://eslint.org/docs/rules/
'_x33' is defined but never used. Open
function installNar(_x32, _x33) {
- Read upRead up
- Exclude checks
Disallow Unused Variables (no-unused-vars)
Variables that are declared and not used anywhere in the code are most likely an error due to incomplete refactoring. Such variables take up space in the code and can lead to confusion by readers.
Rule Details
This rule is aimed at eliminating unused variables, functions, and parameters of functions.
A variable is considered to be used if any of the following are true:
- It represents a function that is called (
doSomething()
) - It is read (
var y = x
) - It is passed into a function as an argument (
doSomething(x)
) - It is read inside of a function that is passed to another function (
doSomething(function() { foo(); })
)
A variable is not considered to be used if it is only ever assigned to (var x = 5
) or declared.
Examples of incorrect code for this rule:
/*eslint no-unused-vars: "error"*/
/*global some_unused_var*/
// It checks variables you have defined as global
some_unused_var = 42;
var x;
// Write-only variables are not considered as used.
var y = 10;
y = 5;
// A read for a modification of itself is not considered as used.
var z = 0;
z = z + 1;
// By default, unused arguments cause warnings.
(function(foo) {
return 5;
})();
// Unused recursive functions also cause warnings.
function fact(n) {
if (n < 2) return 1;
return n * fact(n - 1);
}
// When a function definition destructures an array, unused entries from the array also cause warnings.
function getY([x, y]) {
return y;
}
Examples of correct code for this rule:
/*eslint no-unused-vars: "error"*/
var x = 10;
alert(x);
// foo is considered used here
myFunc(function foo() {
// ...
}.bind(this));
(function(foo) {
return foo;
})();
var myFunc;
myFunc = setTimeout(function() {
// myFunc is considered used
myFunc();
}, 50);
// Only the second argument from the descructured array is used.
function getY([, y]) {
return y;
}
exported
In environments outside of CommonJS or ECMAScript modules, you may use var
to create a global variable that may be used by other scripts. You can use the /* exported variableName */
comment block to indicate that this variable is being exported and therefore should not be considered unused.
Note that /* exported */
has no effect for any of the following:
- when the environment is
node
orcommonjs
- when
parserOptions.sourceType
ismodule
- when
ecmaFeatures.globalReturn
istrue
The line comment // exported variableName
will not work as exported
is not line-specific.
Examples of correct code for /* exported variableName */
operation:
/* exported global_var */
var global_var = 42;
Options
This rule takes one argument which can be a string or an object. The string settings are the same as those of the vars
property (explained below).
By default this rule is enabled with all
option for variables and after-used
for arguments.
{
"rules": {
"no-unused-vars": ["error", { "vars": "all", "args": "after-used", "ignoreRestSiblings": false }]
}
}
vars
The vars
option has two settings:
-
all
checks all variables for usage, including those in the global scope. This is the default setting. -
local
checks only that locally-declared variables are used but will allow global variables to be unused.
vars: local
Examples of correct code for the { "vars": "local" }
option:
/*eslint no-unused-vars: ["error", { "vars": "local" }]*/
/*global some_unused_var */
some_unused_var = 42;
varsIgnorePattern
The varsIgnorePattern
option specifies exceptions not to check for usage: variables whose names match a regexp pattern. For example, variables whose names contain ignored
or Ignored
.
Examples of correct code for the { "varsIgnorePattern": "[iI]gnored" }
option:
/*eslint no-unused-vars: ["error", { "varsIgnorePattern": "[iI]gnored" }]*/
var firstVarIgnored = 1;
var secondVar = 2;
console.log(secondVar);
args
The args
option has three settings:
-
after-used
- only the last argument must be used. This allows you, for instance, to have two named parameters to a function and as long as you use the second argument, ESLint will not warn you about the first. This is the default setting. -
all
- all named arguments must be used. -
none
- do not check arguments.
args: after-used
Examples of incorrect code for the default { "args": "after-used" }
option:
/*eslint no-unused-vars: ["error", { "args": "after-used" }]*/
// 1 error
// "baz" is defined but never used
(function(foo, bar, baz) {
return bar;
})();
Examples of correct code for the default { "args": "after-used" }
option:
/*eslint no-unused-vars: ["error", {"args": "after-used"}]*/
(function(foo, bar, baz) {
return baz;
})();
args: all
Examples of incorrect code for the { "args": "all" }
option:
/*eslint no-unused-vars: ["error", { "args": "all" }]*/
// 2 errors
// "foo" is defined but never used
// "baz" is defined but never used
(function(foo, bar, baz) {
return bar;
})();
args: none
Examples of correct code for the { "args": "none" }
option:
/*eslint no-unused-vars: ["error", { "args": "none" }]*/
(function(foo, bar, baz) {
return bar;
})();
ignoreRestSiblings
The ignoreRestSiblings
option is a boolean (default: false
). Using a Rest Property it is possible to "omit" properties from an object, but by default the sibling properties are marked as "unused". With this option enabled the rest property's siblings are ignored.
Examples of correct code for the { "ignoreRestSiblings": true }
option:
/*eslint no-unused-vars: ["error", { "ignoreRestSiblings": true }]*/
// 'type' is ignored because it has a rest property sibling.
var { type, ...coords } = data;
argsIgnorePattern
The argsIgnorePattern
option specifies exceptions not to check for usage: arguments whose names match a regexp pattern. For example, variables whose names begin with an underscore.
Examples of correct code for the { "argsIgnorePattern": "^_" }
option:
/*eslint no-unused-vars: ["error", { "argsIgnorePattern": "^_" }]*/
function foo(x, _y) {
return x + 1;
}
foo();
caughtErrors
The caughtErrors
option is used for catch
block arguments validation.
It has two settings:
-
none
- do not check error objects. This is the default setting. -
all
- all named arguments must be used.
caughtErrors: none
Not specifying this rule is equivalent of assigning it to none
.
Examples of correct code for the { "caughtErrors": "none" }
option:
/*eslint no-unused-vars: ["error", { "caughtErrors": "none" }]*/
try {
//...
} catch (err) {
console.error("errors");
}
caughtErrors: all
Examples of incorrect code for the { "caughtErrors": "all" }
option:
/*eslint no-unused-vars: ["error", { "caughtErrors": "all" }]*/
// 1 error
// "err" is defined but never used
try {
//...
} catch (err) {
console.error("errors");
}
caughtErrorsIgnorePattern
The caughtErrorsIgnorePattern
option specifies exceptions not to check for usage: catch arguments whose names match a regexp pattern. For example, variables whose names begin with a string 'ignore'.
Examples of correct code for the { "caughtErrorsIgnorePattern": "^ignore" }
option:
/*eslint no-unused-vars: ["error", { "caughtErrorsIgnorePattern": "^ignore" }]*/
try {
//...
} catch (ignoreErr) {
console.error("errors");
}
When Not To Use It
If you don't want to be notified about unused variables or function arguments, you can safely turn this rule off. Source: http://eslint.org/docs/rules/
Unexpected 'this'. Open
return _ref13.apply(this, arguments);
- Read upRead up
- Exclude checks
Disallow this
keywords outside of classes or class-like objects. (no-invalid-this)
Under the strict mode, this
keywords outside of classes or class-like objects might be undefined
and raise a TypeError
.
Rule Details
This rule aims to flag usage of this
keywords outside of classes or class-like objects.
Basically this rule checks whether or not a function which are containing this
keywords is a constructor or a method.
This rule judges from following conditions whether or not the function is a constructor:
- The name of the function starts with uppercase.
- The function is assigned to a variable which starts with an uppercase letter.
- The function is a constructor of ES2015 Classes.
This rule judges from following conditions whether or not the function is a method:
- The function is on an object literal.
- The function is assigned to a property.
- The function is a method/getter/setter of ES2015 Classes. (excepts static methods)
And this rule allows this
keywords in functions below:
- The
call/apply/bind
method of the function is called directly. - The function is a callback of array methods (such as
.forEach()
) ifthisArg
is given. - The function has
@this
tag in its JSDoc comment.
Otherwise are considered problems.
This rule applies only in strict mode.
With "parserOptions": { "sourceType": "module" }
in the ESLint configuration, your code is in strict mode even without a "use strict"
directive.
Examples of incorrect code for this rule in strict mode:
/*eslint no-invalid-this: "error"*/
/*eslint-env es6*/
"use strict";
this.a = 0;
baz(() => this);
(function() {
this.a = 0;
baz(() => this);
})();
function foo() {
this.a = 0;
baz(() => this);
}
var foo = function() {
this.a = 0;
baz(() => this);
};
foo(function() {
this.a = 0;
baz(() => this);
});
obj.foo = () => {
// `this` of arrow functions is the outer scope's.
this.a = 0;
};
var obj = {
aaa: function() {
return function foo() {
// There is in a method `aaa`, but `foo` is not a method.
this.a = 0;
baz(() => this);
};
}
};
foo.forEach(function() {
this.a = 0;
baz(() => this);
});
Examples of correct code for this rule in strict mode:
/*eslint no-invalid-this: "error"*/
/*eslint-env es6*/
"use strict";
function Foo() {
// OK, this is in a legacy style constructor.
this.a = 0;
baz(() => this);
}
class Foo {
constructor() {
// OK, this is in a constructor.
this.a = 0;
baz(() => this);
}
}
var obj = {
foo: function foo() {
// OK, this is in a method (this function is on object literal).
this.a = 0;
}
};
var obj = {
foo() {
// OK, this is in a method (this function is on object literal).
this.a = 0;
}
};
var obj = {
get foo() {
// OK, this is in a method (this function is on object literal).
return this.a;
}
};
var obj = Object.create(null, {
foo: {value: function foo() {
// OK, this is in a method (this function is on object literal).
this.a = 0;
}}
});
Object.defineProperty(obj, "foo", {
value: function foo() {
// OK, this is in a method (this function is on object literal).
this.a = 0;
}
});
Object.defineProperties(obj, {
foo: {value: function foo() {
// OK, this is in a method (this function is on object literal).
this.a = 0;
}}
});
function Foo() {
this.foo = function foo() {
// OK, this is in a method (this function assigns to a property).
this.a = 0;
baz(() => this);
};
}
obj.foo = function foo() {
// OK, this is in a method (this function assigns to a property).
this.a = 0;
};
Foo.prototype.foo = function foo() {
// OK, this is in a method (this function assigns to a property).
this.a = 0;
};
class Foo {
foo() {
// OK, this is in a method.
this.a = 0;
baz(() => this);
}
static foo() {
// OK, this is in a method (static methods also have valid this).
this.a = 0;
baz(() => this);
}
}
var foo = (function foo() {
// OK, the `bind` method of this function is called directly.
this.a = 0;
}).bind(obj);
foo.forEach(function() {
// OK, `thisArg` of `.forEach()` is given.
this.a = 0;
baz(() => this);
}, thisArg);
/** @this Foo */
function foo() {
// OK, this function has a `@this` tag in its JSDoc comment.
this.a = 0;
}
When Not To Use It
If you don't want to be notified about usage of this
keyword outside of classes or class-like objects, you can safely disable this rule.
Source: http://eslint.org/docs/rules/
All 'var' declarations must be at the top of the function scope. Open
var _keys = require('babel-runtime/core-js/object/keys');
- Read upRead up
- Exclude checks
Require Variable Declarations to be at the top of their scope (vars-on-top)
The vars-on-top
rule generates warnings when variable declarations are not used serially at the top of a function scope or the top of a program.
By default variable declarations are always moved (“hoisted”) invisibly to the top of their containing scope by the JavaScript interpreter.
This rule forces the programmer to represent that behaviour by manually moving the variable declaration to the top of its containing scope.
Rule Details
This rule aims to keep all variable declarations in the leading series of statements. Allowing multiple declarations helps promote maintainability and is thus allowed.
Examples of incorrect code for this rule:
/*eslint vars-on-top: "error"*/
// Variable declarations in a block:
function doSomething() {
var first;
if (true) {
first = true;
}
var second;
}
// Variable declaration in for initializer:
function doSomething() {
for (var i=0; i<10; i++) {}
}
/*eslint vars-on-top: "error"*/
// Variables after other statements:
f();
var a;
Examples of correct code for this rule:
/*eslint vars-on-top: "error"*/
function doSomething() {
var first;
var second; //multiple declarations are allowed at the top
if (true) {
first = true;
}
}
function doSomething() {
var i;
for (i=0; i<10; i++) {}
}
/*eslint vars-on-top: "error"*/
var a;
f();
/*eslint vars-on-top: "error"*/
// Directives may precede variable declarations.
"use strict";
var a;
f();
// Comments can describe variables.
function doSomething() {
// this is the first var.
var first;
// this is the second var.
var second
}
Further Reading
Unexpected var, use let or const instead. Open
var balloon = new GhostViewClass.Balloon(directory.asArrayBuffer());
- Read upRead up
- Exclude checks
require let
or const
instead of var
(no-var)
ECMAScript 6 allows programmers to create variables with block scope instead of function scope using the let
and const
keywords. Block scope is common in many other programming languages and helps programmers avoid mistakes
such as:
var count = people.length;
var enoughFood = count > sandwiches.length;
if (enoughFood) {
var count = sandwiches.length; // accidentally overriding the count variable
console.log("We have " + count + " sandwiches for everyone. Plenty for all!");
}
// our count variable is no longer accurate
console.log("We have " + count + " people and " + sandwiches.length + " sandwiches!");
Rule Details
This rule is aimed at discouraging the use of var
and encouraging the use of const
or let
instead.
Examples
Examples of incorrect code for this rule:
/*eslint no-var: "error"*/
var x = "y";
var CONFIG = {};
Examples of correct code for this rule:
/*eslint no-var: "error"*/
/*eslint-env es6*/
let x = "y";
const CONFIG = {};
When Not To Use It
In addition to non-ES6 environments, existing JavaScript projects that are beginning to introduce ES6 into their
codebase may not want to apply this rule if the cost of migrating from var
to let
is too costly.
Source: http://eslint.org/docs/rules/
Expected linebreaks to be 'LF' but found 'CRLF'. Open
* @param {NamedKernel | string} [from] who handled the target? kernel or named id
- Read upRead up
- Exclude checks
enforce consistent linebreak style (linebreak-style)
When developing with a lot of people all having different editors, VCS applications and operating systems it may occur that different line endings are written by either of the mentioned (might especially happen when using the windows and mac versions of SourceTree together).
The linebreaks (new lines) used in windows operating system are usually carriage returns (CR) followed by a line feed (LF) making it a carriage return line feed (CRLF)
whereas Linux and Unix use a simple line feed (LF). The corresponding control sequences are "\n"
(for LF) and "\r\n"
for (CRLF).
Many versioning systems (like git and subversion) can automatically ensure the correct ending. However to cover all contingencies, you can activate this rule.
Rule Details
This rule enforces consistent line endings independent of operating system, VCS, or editor used across your codebase.
Options
This rule has a string option:
-
"unix"
(default) enforces the usage of Unix line endings:\n
for LF. -
"windows"
enforces the usage of Windows line endings:\r\n
for CRLF.
unix
Examples of incorrect code for this rule with the default "unix"
option:
/*eslint linebreak-style: ["error", "unix"]*/
var a = 'a'; // \r\n
Examples of correct code for this rule with the default "unix"
option:
/*eslint linebreak-style: ["error", "unix"]*/
var a = 'a', // \n
b = 'b'; // \n
// \n
function foo(params) { // \n
// do stuff \n
}// \n
windows
Examples of incorrect code for this rule with the "windows"
option:
/*eslint linebreak-style: ["error", "windows"]*/
var a = 'a'; // \n
Examples of correct code for this rule with the "windows"
option:
/*eslint linebreak-style: ["error", "windows"]*/
var a = 'a', // \r\n
b = 'b'; // \r\n
// \r\n
function foo(params) { // \r\n
// do stuff \r\n
} // \r\n
Using this rule with version control systems
Version control systems sometimes have special behavior for linebreaks. To make it easy for developers to contribute to your codebase from different platforms, you may want to configure your VCS to handle linebreaks appropriately.
For example, the default behavior of git on Windows systems is to convert LF linebreaks to CRLF when checking out files, but to store the linebreaks as LF when committing a change. This will cause the linebreak-style
rule to report errors if configured with the "unix"
setting, because the files that ESLint sees will have CRLF linebreaks. If you use git, you may want to add a line to your .gitattributes
file to prevent git from converting linebreaks in .js
files:
*.js text eol=lf
When Not To Use It
If you aren't concerned about having different line endings within your code, then you can safely turn this rule off.
Compatibility
- JSCS: validateLineBreaks Source: http://eslint.org/docs/rules/
Unexpected function expression. Open
install_results.forEach(function (install_result) {
- Read upRead up
- Exclude checks
Suggest using arrow functions as callbacks. (prefer-arrow-callback)
Arrow functions are suited to callbacks, because:
-
this
keywords in arrow functions bind to the upper scope's. - The notation of the arrow function is shorter than function expression's.
Rule Details
This rule is aimed to flag usage of function expressions in an argument list.
The following patterns are considered problems:
/*eslint prefer-arrow-callback: "error"*/
foo(function(a) { return a; });
foo(function() { return this.a; }.bind(this));
The following patterns are not considered problems:
/*eslint prefer-arrow-callback: "error"*/
/*eslint-env es6*/
foo(a => a);
foo(function*() { yield; });
// this is not a callback.
var foo = function foo(a) { return a; };
// using `this` without `.bind(this)`.
foo(function() { return this.a; });
// recursively.
foo(function bar(n) { return n && n + bar(n - 1); });
Options
This rule takes one optional argument, an object which is an options object.
allowNamedFunctions
This is a boolean
option and it is false
by default. When set to true
, the rule doesn't warn on named functions used as callbacks.
Examples of correct code for the { "allowNamedFunctions": true }
option:
/*eslint prefer-arrow-callback: ["error", { "allowNamedFunctions": true }]*/
foo(function bar() {});
allowUnboundThis
This is a boolean
option and it is true
by default. When set to false
, this option allows the use of this
without restriction and checks for dynamically assigned this
values such as when using Array.prototype.map
with a context
argument. Normally, the rule will flag the use of this
whenever a function does not use bind()
to specify the value of this
constantly.
Examples of incorrect code for the { "allowUnboundThis": false }
option:
/*eslint prefer-arrow-callback: ["error", { "allowUnboundThis": false }]*/
/*eslint-env es6*/
foo(function() { this.a; });
foo(function() { (() => this); });
someArray.map(function (itm) { return this.doSomething(itm); }, someObject);
When Not To Use It
This rule should not be used in ES3/5 environments.
In ES2015 (ES6) or later, if you don't want to be notified about function expressions in an argument list, you can safely disable this rule. Source: http://eslint.org/docs/rules/
No magic number: 36. Open
case 36:
- Read upRead up
- Exclude checks
Disallow Magic Numbers (no-magic-numbers)
'Magic numbers' are numbers that occur multiple time in code without an explicit meaning. They should preferably be replaced by named constants.
var now = Date.now(),
inOneHour = now + (60 * 60 * 1000);
Rule Details
The no-magic-numbers
rule aims to make code more readable and refactoring easier by ensuring that special numbers
are declared as constants to make their meaning explicit.
Examples of incorrect code for this rule:
/*eslint no-magic-numbers: "error"*/
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * 0.25);
/*eslint no-magic-numbers: "error"*/
var data = ['foo', 'bar', 'baz'];
var dataLast = data[2];
/*eslint no-magic-numbers: "error"*/
var SECONDS;
SECONDS = 60;
Examples of correct code for this rule:
/*eslint no-magic-numbers: "error"*/
var TAX = 0.25;
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * TAX);
Options
ignore
An array of numbers to ignore. It's set to []
by default.
If provided, it must be an Array
.
Examples of correct code for the sample { "ignore": [1] }
option:
/*eslint no-magic-numbers: ["error", { "ignore": [1] }]*/
var data = ['foo', 'bar', 'baz'];
var dataLast = data.length && data[data.length - 1];
ignoreArrayIndexes
A boolean to specify if numbers used as array indexes are considered okay. false
by default.
Examples of correct code for the { "ignoreArrayIndexes": true }
option:
/*eslint no-magic-numbers: ["error", { "ignoreArrayIndexes": true }]*/
var data = ['foo', 'bar', 'baz'];
var dataLast = data[2];
enforceConst
A boolean to specify if we should check for the const keyword in variable declaration of numbers. false
by default.
Examples of incorrect code for the { "enforceConst": true }
option:
/*eslint no-magic-numbers: ["error", { "enforceConst": true }]*/
var TAX = 0.25;
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * TAX);
detectObjects
A boolean to specify if we should detect numbers when setting object properties for example. false
by default.
Examples of incorrect code for the { "detectObjects": true }
option:
/*eslint no-magic-numbers: ["error", { "detectObjects": true }]*/
var magic = {
tax: 0.25
};
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * magic.tax);
Examples of correct code for the { "detectObjects": true }
option:
/*eslint no-magic-numbers: ["error", { "detectObjects": true }]*/
var TAX = 0.25;
var magic = {
tax: TAX
};
var dutyFreePrice = 100,
finalPrice = dutyFreePrice + (dutyFreePrice * magic.tax);
Source: http://eslint.org/docs/rules/
Assignment to property of function parameter '_context11'. Open
_context11.t0 = _context11['catch'](3);
- Read upRead up
- Exclude checks
Disallow Reassignment of Function Parameters (no-param-reassign)
Assignment to variables declared as function parameters can be misleading and lead to confusing behavior, as modifying function parameters will also mutate the arguments
object. Often, assignment to function parameters is unintended and indicative of a mistake or programmer error.
This rule can be also configured to fail when function parameters are modified. Side effects on parameters can cause counter-intuitive execution flow and make errors difficult to track down.
Rule Details
This rule aims to prevent unintended behavior caused by modification or reassignment of function parameters.
Examples of incorrect code for this rule:
/*eslint no-param-reassign: "error"*/
function foo(bar) {
bar = 13;
}
function foo(bar) {
bar++;
}
Examples of correct code for this rule:
/*eslint no-param-reassign: "error"*/
function foo(bar) {
var baz = bar;
}
Options
This rule takes one option, an object, with a boolean property "props"
and an array "ignorePropertyModificationsFor"
. "props"
is false
by default. If "props"
is set to true
, this rule warns against the modification of parameter properties unless they're included in "ignorePropertyModificationsFor"
, which is an empty array by default.
props
Examples of correct code for the default { "props": false }
option:
/*eslint no-param-reassign: ["error", { "props": false }]*/
function foo(bar) {
bar.prop = "value";
}
function foo(bar) {
delete bar.aaa;
}
function foo(bar) {
bar.aaa++;
}
Examples of incorrect code for the { "props": true }
option:
/*eslint no-param-reassign: ["error", { "props": true }]*/
function foo(bar) {
bar.prop = "value";
}
function foo(bar) {
delete bar.aaa;
}
function foo(bar) {
bar.aaa++;
}
Examples of correct code for the { "props": true }
option with "ignorePropertyModificationsFor"
set:
/*eslint no-param-reassign: ["error", { "props": true, "ignorePropertyModificationsFor": ["bar"] }]*/
function foo(bar) {
bar.prop = "value";
}
function foo(bar) {
delete bar.aaa;
}
function foo(bar) {
bar.aaa++;
}
When Not To Use It
If you want to allow assignment to function parameters, then you can safely disable this rule.
Further Reading
Missing JSDoc comment. Open
function installNar(_x32, _x33) {
- Read upRead up
- Exclude checks
require JSDoc comments (require-jsdoc)
JSDoc is a JavaScript API documentation generator. It uses specially-formatted comments inside of code to generate API documentation automatically. For example, this is what a JSDoc comment looks like for a function:
/**
* Adds two numbers together.
* @param {int} num1 The first number.
* @param {int} num2 The second number.
* @returns {int} The sum of the two numbers.
*/
function sum(num1, num2) {
return num1 + num2;
}
Some style guides require JSDoc comments for all functions as a way of explaining function behavior.
Rule Details
This rule requires JSDoc comments for specified nodes. Supported nodes:
"FunctionDeclaration"
"ClassDeclaration"
"MethodDefinition"
"ArrowFunctionExpression"
Options
This rule has a single object option:
-
"require"
requires JSDoc comments for the specified nodes
Default option settings are:
{
"require-jsdoc": ["error", {
"require": {
"FunctionDeclaration": true,
"MethodDefinition": false,
"ClassDeclaration": false,
"ArrowFunctionExpression": false
}
}]
}
require
Examples of incorrect code for this rule with the { "require": { "FunctionDeclaration": true, "MethodDefinition": true, "ClassDeclaration": true, "ArrowFunctionExpression": true } }
option:
/*eslint "require-jsdoc": ["error", {
"require": {
"FunctionDeclaration": true,
"MethodDefinition": true,
"ClassDeclaration": true
}
}]*/
function foo() {
return 10;
}
var foo = () => {
return 10;
}
class Test{
getDate(){}
}
Examples of correct code for this rule with the { "require": { "FunctionDeclaration": true, "MethodDefinition": true, "ClassDeclaration": true, "ArrowFunctionExpression": true } }
option:
/*eslint "require-jsdoc": ["error", {
"require": {
"FunctionDeclaration": true,
"MethodDefinition": true,
"ClassDeclaration": true
}
}]*/
/**
* It returns 10
*/
function foo() {
return 10;
}
/**
* It returns test + 10
* @params {int} test - some number
* @returns {int} sum of test and 10
*/
var foo = (test) => {
return test + 10;
}
/**
* It returns 10
*/
var foo = () => {
return 10;
}
/**
* It returns 10
*/
var foo = function() {
return 10;
}
var array = [1,2,3];
array.filter(function(item) {
return item > 2;
});
/**
* It returns 10
*/
class Test{
/**
* returns the date
*/
getDate(){}
}
setTimeout(() => {}, 10); // since it's an anonymous arrow function
When Not To Use It
If you do not require JSDoc for your functions, then you can leave this rule off.
Related Rules
- [valid-jsdoc](valid-jsdoc.md) Source: http://eslint.org/docs/rules/
Expected linebreaks to be 'LF' but found 'CRLF'. Open
/**
- Read upRead up
- Exclude checks
enforce consistent linebreak style (linebreak-style)
When developing with a lot of people all having different editors, VCS applications and operating systems it may occur that different line endings are written by either of the mentioned (might especially happen when using the windows and mac versions of SourceTree together).
The linebreaks (new lines) used in windows operating system are usually carriage returns (CR) followed by a line feed (LF) making it a carriage return line feed (CRLF)
whereas Linux and Unix use a simple line feed (LF). The corresponding control sequences are "\n"
(for LF) and "\r\n"
for (CRLF).
Many versioning systems (like git and subversion) can automatically ensure the correct ending. However to cover all contingencies, you can activate this rule.
Rule Details
This rule enforces consistent line endings independent of operating system, VCS, or editor used across your codebase.
Options
This rule has a string option:
-
"unix"
(default) enforces the usage of Unix line endings:\n
for LF. -
"windows"
enforces the usage of Windows line endings:\r\n
for CRLF.
unix
Examples of incorrect code for this rule with the default "unix"
option:
/*eslint linebreak-style: ["error", "unix"]*/
var a = 'a'; // \r\n
Examples of correct code for this rule with the default "unix"
option:
/*eslint linebreak-style: ["error", "unix"]*/
var a = 'a', // \n
b = 'b'; // \n
// \n
function foo(params) { // \n
// do stuff \n
}// \n
windows
Examples of incorrect code for this rule with the "windows"
option:
/*eslint linebreak-style: ["error", "windows"]*/
var a = 'a'; // \n
Examples of correct code for this rule with the "windows"
option:
/*eslint linebreak-style: ["error", "windows"]*/
var a = 'a', // \r\n
b = 'b'; // \r\n
// \r\n
function foo(params) { // \r\n
// do stuff \r\n
} // \r\n
Using this rule with version control systems
Version control systems sometimes have special behavior for linebreaks. To make it easy for developers to contribute to your codebase from different platforms, you may want to configure your VCS to handle linebreaks appropriately.
For example, the default behavior of git on Windows systems is to convert LF linebreaks to CRLF when checking out files, but to store the linebreaks as LF when committing a change. This will cause the linebreak-style
rule to report errors if configured with the "unix"
setting, because the files that ESLint sees will have CRLF linebreaks. If you use git, you may want to add a line to your .gitattributes
file to prevent git from converting linebreaks in .js
files:
*.js text eol=lf
When Not To Use It
If you aren't concerned about having different line endings within your code, then you can safely turn this rule off.
Compatibility
- JSCS: validateLineBreaks Source: http://eslint.org/docs/rules/
Assignment to property of function parameter '_context11'. Open
_context11.prev = 3;
- Read upRead up
- Exclude checks
Disallow Reassignment of Function Parameters (no-param-reassign)
Assignment to variables declared as function parameters can be misleading and lead to confusing behavior, as modifying function parameters will also mutate the arguments
object. Often, assignment to function parameters is unintended and indicative of a mistake or programmer error.
This rule can be also configured to fail when function parameters are modified. Side effects on parameters can cause counter-intuitive execution flow and make errors difficult to track down.
Rule Details
This rule aims to prevent unintended behavior caused by modification or reassignment of function parameters.
Examples of incorrect code for this rule:
/*eslint no-param-reassign: "error"*/
function foo(bar) {
bar = 13;
}
function foo(bar) {
bar++;
}
Examples of correct code for this rule:
/*eslint no-param-reassign: "error"*/
function foo(bar) {
var baz = bar;
}
Options
This rule takes one option, an object, with a boolean property "props"
and an array "ignorePropertyModificationsFor"
. "props"
is false
by default. If "props"
is set to true
, this rule warns against the modification of parameter properties unless they're included in "ignorePropertyModificationsFor"
, which is an empty array by default.
props
Examples of correct code for the default { "props": false }
option:
/*eslint no-param-reassign: ["error", { "props": false }]*/
function foo(bar) {
bar.prop = "value";
}
function foo(bar) {
delete bar.aaa;
}
function foo(bar) {
bar.aaa++;
}
Examples of incorrect code for the { "props": true }
option:
/*eslint no-param-reassign: ["error", { "props": true }]*/
function foo(bar) {
bar.prop = "value";
}
function foo(bar) {
delete bar.aaa;
}
function foo(bar) {
bar.aaa++;
}
Examples of correct code for the { "props": true }
option with "ignorePropertyModificationsFor"
set:
/*eslint no-param-reassign: ["error", { "props": true, "ignorePropertyModificationsFor": ["bar"] }]*/
function foo(bar) {
bar.prop = "value";
}
function foo(bar) {
delete bar.aaa;
}
function foo(bar) {
bar.aaa++;
}
When Not To Use It
If you want to allow assignment to function parameters, then you can safely disable this rule.
Further Reading
Assignment to property of function parameter '_context11'. Open
_context11.next = 22;
- Read upRead up
- Exclude checks
Disallow Reassignment of Function Parameters (no-param-reassign)
Assignment to variables declared as function parameters can be misleading and lead to confusing behavior, as modifying function parameters will also mutate the arguments
object. Often, assignment to function parameters is unintended and indicative of a mistake or programmer error.
This rule can be also configured to fail when function parameters are modified. Side effects on parameters can cause counter-intuitive execution flow and make errors difficult to track down.
Rule Details
This rule aims to prevent unintended behavior caused by modification or reassignment of function parameters.
Examples of incorrect code for this rule:
/*eslint no-param-reassign: "error"*/
function foo(bar) {
bar = 13;
}
function foo(bar) {
bar++;
}
Examples of correct code for this rule:
/*eslint no-param-reassign: "error"*/
function foo(bar) {
var baz = bar;
}
Options
This rule takes one option, an object, with a boolean property "props"
and an array "ignorePropertyModificationsFor"
. "props"
is false
by default. If "props"
is set to true
, this rule warns against the modification of parameter properties unless they're included in "ignorePropertyModificationsFor"
, which is an empty array by default.
props
Examples of correct code for the default { "props": false }
option:
/*eslint no-param-reassign: ["error", { "props": false }]*/
function foo(bar) {
bar.prop = "value";
}
function foo(bar) {
delete bar.aaa;
}
function foo(bar) {
bar.aaa++;
}
Examples of incorrect code for the { "props": true }
option:
/*eslint no-param-reassign: ["error", { "props": true }]*/
function foo(bar) {
bar.prop = "value";
}
function foo(bar) {
delete bar.aaa;
}
function foo(bar) {
bar.aaa++;
}
Examples of correct code for the { "props": true }
option with "ignorePropertyModificationsFor"
set:
/*eslint no-param-reassign: ["error", { "props": true, "ignorePropertyModificationsFor": ["bar"] }]*/
function foo(bar) {
bar.prop = "value";
}
function foo(bar) {
delete bar.aaa;
}
function foo(bar) {
bar.aaa++;
}
When Not To Use It
If you want to allow assignment to function parameters, then you can safely disable this rule.