Properties shouldn't be quoted as all quotes are redundant. Open
"maps":'.maps/'
- Read upRead up
- Exclude checks
require quotes around object literal property names (quote-props)
Object literal property names can be defined in two ways: using literals or using strings. For example, these two objects are equivalent:
var object1 = {
property: true
};
var object2 = {
"property": true
};
In many cases, it doesn't matter if you choose to use an identifier instead of a string or vice-versa. Even so, you might decide to enforce a consistent style in your code.
There are, however, some occasions when you must use quotes:
- If you are using an ECMAScript 3 JavaScript engine (such as IE8) and you want to use a keyword (such as
if
) as a property name. This restriction was removed in ECMAScript 5. - You want to use a non-identifier character in your property name, such as having a property with a space like
"one two"
.
Another example where quotes do matter is when using numeric literals as property keys:
var object = {
1e2: 1,
100: 2
};
This may look alright at first sight, but this code in fact throws a syntax error in ECMAScript 5 strict mode. This happens because 1e2
and 100
are coerced into strings before getting used as the property name. Both String(1e2)
and String(100)
happen to be equal to "100"
, which causes the "Duplicate data property in object literal not allowed in strict mode" error. Issues like that can be tricky to debug, so some prefer to require quotes around all property names.
Rule Details
This rule requires quotes around object literal property names.
Options
This rule has two options, a string option and an object option.
String option:
-
"always"
(default) requires quotes around all object literal property names -
"as-needed"
disallows quotes around object literal property names that are not strictly required -
"consistent"
enforces a consistent quote style requires quotes around object literal property names -
"consistent-as-needed"
requires quotes around all object literal property names if any name strictly requires quotes, otherwise disallows quotes around object property names
Object option:
-
"keywords": true
requires quotes around language keywords used as object property names (only applies when usingas-needed
orconsistent-as-needed
) -
"unnecessary": true
(default) disallows quotes around object literal property names that are not strictly required (only applies when usingas-needed
) -
"unnecessary": false
allows quotes around object literal property names that are not strictly required (only applies when usingas-needed
) -
"numbers": true
requires quotes around numbers used as object property names (only applies when usingas-needed
)
always
Examples of incorrect code for this rule with the default "always"
option:
/*eslint quote-props: ["error", "always"]*/
var object = {
foo: "bar",
baz: 42,
"qux-lorem": true
};
Examples of correct code for this rule with the default "always"
option:
/*eslint quote-props: ["error", "always"]*/
/*eslint-env es6*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42,
'qux-lorem': true
};
var object3 = {
foo() {
return;
}
};
as-needed
Examples of incorrect code for this rule with the "as-needed"
option:
/*eslint quote-props: ["error", "as-needed"]*/
var object = {
"a": 0,
"0": 0,
"true": 0,
"null": 0
};
Examples of correct code for this rule with the "as-needed"
option:
/*eslint quote-props: ["error", "as-needed"]*/
/*eslint-env es6*/
var object1 = {
"a-b": 0,
"0x0": 0,
"1e2": 0
};
var object2 = {
foo: 'bar',
baz: 42,
true: 0,
0: 0,
'qux-lorem': true
};
var object3 = {
foo() {
return;
}
};
consistent
Examples of incorrect code for this rule with the "consistent"
option:
/*eslint quote-props: ["error", "consistent"]*/
var object1 = {
foo: "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
baz: 42
};
Examples of correct code for this rule with the "consistent"
option:
/*eslint quote-props: ["error", "consistent"]*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42
};
var object3 = {
foo: 'bar',
baz: 42
};
consistent-as-needed
Examples of incorrect code for this rule with the "consistent-as-needed"
option:
/*eslint quote-props: ["error", "consistent-as-needed"]*/
var object1 = {
foo: "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42
};
Examples of correct code for this rule with the "consistent-as-needed"
option:
/*eslint quote-props: ["error", "consistent-as-needed"]*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
foo: 'bar',
baz: 42
};
keywords
Examples of additional incorrect code for this rule with the "as-needed", { "keywords": true }
options:
/*eslint quote-props: ["error", "as-needed", { "keywords": true }]*/
var x = {
while: 1,
volatile: "foo"
};
Examples of additional incorrect code for this rule with the "consistent-as-needed", { "keywords": true }
options:
/*eslint quote-props: ["error", "consistent-as-needed", { "keywords": true }]*/
var x = {
"prop": 1,
"bar": "foo"
};
unnecessary
Examples of additional correct code for this rule with the "as-needed", { "unnecessary": false }
options:
/*eslint quote-props: ["error", "as-needed", { "keywords": true, "unnecessary": false }]*/
var x = {
"while": 1,
"foo": "bar" // Would normally have caused a warning
};
numbers
Examples of additional incorrect code for this rule with the "as-needed", { "numbers": true }
options:
/*eslint quote-props: ["error", "as-needed", { "numbers": true }]*/
var x = {
100: 1
}
When Not To Use It
If you don't care if property names are consistently wrapped in quotes or not, and you don't target legacy ES3 environments, turn this rule off.
Further Reading
Properties shouldn't be quoted as all quotes are redundant. Open
"src": 'src/*.es7.js',
- Read upRead up
- Exclude checks
require quotes around object literal property names (quote-props)
Object literal property names can be defined in two ways: using literals or using strings. For example, these two objects are equivalent:
var object1 = {
property: true
};
var object2 = {
"property": true
};
In many cases, it doesn't matter if you choose to use an identifier instead of a string or vice-versa. Even so, you might decide to enforce a consistent style in your code.
There are, however, some occasions when you must use quotes:
- If you are using an ECMAScript 3 JavaScript engine (such as IE8) and you want to use a keyword (such as
if
) as a property name. This restriction was removed in ECMAScript 5. - You want to use a non-identifier character in your property name, such as having a property with a space like
"one two"
.
Another example where quotes do matter is when using numeric literals as property keys:
var object = {
1e2: 1,
100: 2
};
This may look alright at first sight, but this code in fact throws a syntax error in ECMAScript 5 strict mode. This happens because 1e2
and 100
are coerced into strings before getting used as the property name. Both String(1e2)
and String(100)
happen to be equal to "100"
, which causes the "Duplicate data property in object literal not allowed in strict mode" error. Issues like that can be tricky to debug, so some prefer to require quotes around all property names.
Rule Details
This rule requires quotes around object literal property names.
Options
This rule has two options, a string option and an object option.
String option:
-
"always"
(default) requires quotes around all object literal property names -
"as-needed"
disallows quotes around object literal property names that are not strictly required -
"consistent"
enforces a consistent quote style requires quotes around object literal property names -
"consistent-as-needed"
requires quotes around all object literal property names if any name strictly requires quotes, otherwise disallows quotes around object property names
Object option:
-
"keywords": true
requires quotes around language keywords used as object property names (only applies when usingas-needed
orconsistent-as-needed
) -
"unnecessary": true
(default) disallows quotes around object literal property names that are not strictly required (only applies when usingas-needed
) -
"unnecessary": false
allows quotes around object literal property names that are not strictly required (only applies when usingas-needed
) -
"numbers": true
requires quotes around numbers used as object property names (only applies when usingas-needed
)
always
Examples of incorrect code for this rule with the default "always"
option:
/*eslint quote-props: ["error", "always"]*/
var object = {
foo: "bar",
baz: 42,
"qux-lorem": true
};
Examples of correct code for this rule with the default "always"
option:
/*eslint quote-props: ["error", "always"]*/
/*eslint-env es6*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42,
'qux-lorem': true
};
var object3 = {
foo() {
return;
}
};
as-needed
Examples of incorrect code for this rule with the "as-needed"
option:
/*eslint quote-props: ["error", "as-needed"]*/
var object = {
"a": 0,
"0": 0,
"true": 0,
"null": 0
};
Examples of correct code for this rule with the "as-needed"
option:
/*eslint quote-props: ["error", "as-needed"]*/
/*eslint-env es6*/
var object1 = {
"a-b": 0,
"0x0": 0,
"1e2": 0
};
var object2 = {
foo: 'bar',
baz: 42,
true: 0,
0: 0,
'qux-lorem': true
};
var object3 = {
foo() {
return;
}
};
consistent
Examples of incorrect code for this rule with the "consistent"
option:
/*eslint quote-props: ["error", "consistent"]*/
var object1 = {
foo: "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
baz: 42
};
Examples of correct code for this rule with the "consistent"
option:
/*eslint quote-props: ["error", "consistent"]*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42
};
var object3 = {
foo: 'bar',
baz: 42
};
consistent-as-needed
Examples of incorrect code for this rule with the "consistent-as-needed"
option:
/*eslint quote-props: ["error", "consistent-as-needed"]*/
var object1 = {
foo: "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42
};
Examples of correct code for this rule with the "consistent-as-needed"
option:
/*eslint quote-props: ["error", "consistent-as-needed"]*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
foo: 'bar',
baz: 42
};
keywords
Examples of additional incorrect code for this rule with the "as-needed", { "keywords": true }
options:
/*eslint quote-props: ["error", "as-needed", { "keywords": true }]*/
var x = {
while: 1,
volatile: "foo"
};
Examples of additional incorrect code for this rule with the "consistent-as-needed", { "keywords": true }
options:
/*eslint quote-props: ["error", "consistent-as-needed", { "keywords": true }]*/
var x = {
"prop": 1,
"bar": "foo"
};
unnecessary
Examples of additional correct code for this rule with the "as-needed", { "unnecessary": false }
options:
/*eslint quote-props: ["error", "as-needed", { "keywords": true, "unnecessary": false }]*/
var x = {
"while": 1,
"foo": "bar" // Would normally have caused a warning
};
numbers
Examples of additional incorrect code for this rule with the "as-needed", { "numbers": true }
options:
/*eslint quote-props: ["error", "as-needed", { "numbers": true }]*/
var x = {
100: 1
}
When Not To Use It
If you don't care if property names are consistently wrapped in quotes or not, and you don't target legacy ES3 environments, turn this rule off.
Further Reading
Properties shouldn't be quoted as all quotes are redundant. Open
"tst":{
- Read upRead up
- Exclude checks
require quotes around object literal property names (quote-props)
Object literal property names can be defined in two ways: using literals or using strings. For example, these two objects are equivalent:
var object1 = {
property: true
};
var object2 = {
"property": true
};
In many cases, it doesn't matter if you choose to use an identifier instead of a string or vice-versa. Even so, you might decide to enforce a consistent style in your code.
There are, however, some occasions when you must use quotes:
- If you are using an ECMAScript 3 JavaScript engine (such as IE8) and you want to use a keyword (such as
if
) as a property name. This restriction was removed in ECMAScript 5. - You want to use a non-identifier character in your property name, such as having a property with a space like
"one two"
.
Another example where quotes do matter is when using numeric literals as property keys:
var object = {
1e2: 1,
100: 2
};
This may look alright at first sight, but this code in fact throws a syntax error in ECMAScript 5 strict mode. This happens because 1e2
and 100
are coerced into strings before getting used as the property name. Both String(1e2)
and String(100)
happen to be equal to "100"
, which causes the "Duplicate data property in object literal not allowed in strict mode" error. Issues like that can be tricky to debug, so some prefer to require quotes around all property names.
Rule Details
This rule requires quotes around object literal property names.
Options
This rule has two options, a string option and an object option.
String option:
-
"always"
(default) requires quotes around all object literal property names -
"as-needed"
disallows quotes around object literal property names that are not strictly required -
"consistent"
enforces a consistent quote style requires quotes around object literal property names -
"consistent-as-needed"
requires quotes around all object literal property names if any name strictly requires quotes, otherwise disallows quotes around object property names
Object option:
-
"keywords": true
requires quotes around language keywords used as object property names (only applies when usingas-needed
orconsistent-as-needed
) -
"unnecessary": true
(default) disallows quotes around object literal property names that are not strictly required (only applies when usingas-needed
) -
"unnecessary": false
allows quotes around object literal property names that are not strictly required (only applies when usingas-needed
) -
"numbers": true
requires quotes around numbers used as object property names (only applies when usingas-needed
)
always
Examples of incorrect code for this rule with the default "always"
option:
/*eslint quote-props: ["error", "always"]*/
var object = {
foo: "bar",
baz: 42,
"qux-lorem": true
};
Examples of correct code for this rule with the default "always"
option:
/*eslint quote-props: ["error", "always"]*/
/*eslint-env es6*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42,
'qux-lorem': true
};
var object3 = {
foo() {
return;
}
};
as-needed
Examples of incorrect code for this rule with the "as-needed"
option:
/*eslint quote-props: ["error", "as-needed"]*/
var object = {
"a": 0,
"0": 0,
"true": 0,
"null": 0
};
Examples of correct code for this rule with the "as-needed"
option:
/*eslint quote-props: ["error", "as-needed"]*/
/*eslint-env es6*/
var object1 = {
"a-b": 0,
"0x0": 0,
"1e2": 0
};
var object2 = {
foo: 'bar',
baz: 42,
true: 0,
0: 0,
'qux-lorem': true
};
var object3 = {
foo() {
return;
}
};
consistent
Examples of incorrect code for this rule with the "consistent"
option:
/*eslint quote-props: ["error", "consistent"]*/
var object1 = {
foo: "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
baz: 42
};
Examples of correct code for this rule with the "consistent"
option:
/*eslint quote-props: ["error", "consistent"]*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42
};
var object3 = {
foo: 'bar',
baz: 42
};
consistent-as-needed
Examples of incorrect code for this rule with the "consistent-as-needed"
option:
/*eslint quote-props: ["error", "consistent-as-needed"]*/
var object1 = {
foo: "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42
};
Examples of correct code for this rule with the "consistent-as-needed"
option:
/*eslint quote-props: ["error", "consistent-as-needed"]*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
foo: 'bar',
baz: 42
};
keywords
Examples of additional incorrect code for this rule with the "as-needed", { "keywords": true }
options:
/*eslint quote-props: ["error", "as-needed", { "keywords": true }]*/
var x = {
while: 1,
volatile: "foo"
};
Examples of additional incorrect code for this rule with the "consistent-as-needed", { "keywords": true }
options:
/*eslint quote-props: ["error", "consistent-as-needed", { "keywords": true }]*/
var x = {
"prop": 1,
"bar": "foo"
};
unnecessary
Examples of additional correct code for this rule with the "as-needed", { "unnecessary": false }
options:
/*eslint quote-props: ["error", "as-needed", { "keywords": true, "unnecessary": false }]*/
var x = {
"while": 1,
"foo": "bar" // Would normally have caused a warning
};
numbers
Examples of additional incorrect code for this rule with the "as-needed", { "numbers": true }
options:
/*eslint quote-props: ["error", "as-needed", { "numbers": true }]*/
var x = {
100: 1
}
When Not To Use It
If you don't care if property names are consistently wrapped in quotes or not, and you don't target legacy ES3 environments, turn this rule off.
Further Reading
Properties shouldn't be quoted as all quotes are redundant. Open
"dst": './',
- Read upRead up
- Exclude checks
require quotes around object literal property names (quote-props)
Object literal property names can be defined in two ways: using literals or using strings. For example, these two objects are equivalent:
var object1 = {
property: true
};
var object2 = {
"property": true
};
In many cases, it doesn't matter if you choose to use an identifier instead of a string or vice-versa. Even so, you might decide to enforce a consistent style in your code.
There are, however, some occasions when you must use quotes:
- If you are using an ECMAScript 3 JavaScript engine (such as IE8) and you want to use a keyword (such as
if
) as a property name. This restriction was removed in ECMAScript 5. - You want to use a non-identifier character in your property name, such as having a property with a space like
"one two"
.
Another example where quotes do matter is when using numeric literals as property keys:
var object = {
1e2: 1,
100: 2
};
This may look alright at first sight, but this code in fact throws a syntax error in ECMAScript 5 strict mode. This happens because 1e2
and 100
are coerced into strings before getting used as the property name. Both String(1e2)
and String(100)
happen to be equal to "100"
, which causes the "Duplicate data property in object literal not allowed in strict mode" error. Issues like that can be tricky to debug, so some prefer to require quotes around all property names.
Rule Details
This rule requires quotes around object literal property names.
Options
This rule has two options, a string option and an object option.
String option:
-
"always"
(default) requires quotes around all object literal property names -
"as-needed"
disallows quotes around object literal property names that are not strictly required -
"consistent"
enforces a consistent quote style requires quotes around object literal property names -
"consistent-as-needed"
requires quotes around all object literal property names if any name strictly requires quotes, otherwise disallows quotes around object property names
Object option:
-
"keywords": true
requires quotes around language keywords used as object property names (only applies when usingas-needed
orconsistent-as-needed
) -
"unnecessary": true
(default) disallows quotes around object literal property names that are not strictly required (only applies when usingas-needed
) -
"unnecessary": false
allows quotes around object literal property names that are not strictly required (only applies when usingas-needed
) -
"numbers": true
requires quotes around numbers used as object property names (only applies when usingas-needed
)
always
Examples of incorrect code for this rule with the default "always"
option:
/*eslint quote-props: ["error", "always"]*/
var object = {
foo: "bar",
baz: 42,
"qux-lorem": true
};
Examples of correct code for this rule with the default "always"
option:
/*eslint quote-props: ["error", "always"]*/
/*eslint-env es6*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42,
'qux-lorem': true
};
var object3 = {
foo() {
return;
}
};
as-needed
Examples of incorrect code for this rule with the "as-needed"
option:
/*eslint quote-props: ["error", "as-needed"]*/
var object = {
"a": 0,
"0": 0,
"true": 0,
"null": 0
};
Examples of correct code for this rule with the "as-needed"
option:
/*eslint quote-props: ["error", "as-needed"]*/
/*eslint-env es6*/
var object1 = {
"a-b": 0,
"0x0": 0,
"1e2": 0
};
var object2 = {
foo: 'bar',
baz: 42,
true: 0,
0: 0,
'qux-lorem': true
};
var object3 = {
foo() {
return;
}
};
consistent
Examples of incorrect code for this rule with the "consistent"
option:
/*eslint quote-props: ["error", "consistent"]*/
var object1 = {
foo: "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
baz: 42
};
Examples of correct code for this rule with the "consistent"
option:
/*eslint quote-props: ["error", "consistent"]*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42
};
var object3 = {
foo: 'bar',
baz: 42
};
consistent-as-needed
Examples of incorrect code for this rule with the "consistent-as-needed"
option:
/*eslint quote-props: ["error", "consistent-as-needed"]*/
var object1 = {
foo: "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42
};
Examples of correct code for this rule with the "consistent-as-needed"
option:
/*eslint quote-props: ["error", "consistent-as-needed"]*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
foo: 'bar',
baz: 42
};
keywords
Examples of additional incorrect code for this rule with the "as-needed", { "keywords": true }
options:
/*eslint quote-props: ["error", "as-needed", { "keywords": true }]*/
var x = {
while: 1,
volatile: "foo"
};
Examples of additional incorrect code for this rule with the "consistent-as-needed", { "keywords": true }
options:
/*eslint quote-props: ["error", "consistent-as-needed", { "keywords": true }]*/
var x = {
"prop": 1,
"bar": "foo"
};
unnecessary
Examples of additional correct code for this rule with the "as-needed", { "unnecessary": false }
options:
/*eslint quote-props: ["error", "as-needed", { "keywords": true, "unnecessary": false }]*/
var x = {
"while": 1,
"foo": "bar" // Would normally have caused a warning
};
numbers
Examples of additional incorrect code for this rule with the "as-needed", { "numbers": true }
options:
/*eslint quote-props: ["error", "as-needed", { "numbers": true }]*/
var x = {
100: 1
}
When Not To Use It
If you don't care if property names are consistently wrapped in quotes or not, and you don't target legacy ES3 environments, turn this rule off.
Further Reading
Properties shouldn't be quoted as all quotes are redundant. Open
"main":'tst/index.js'
- Read upRead up
- Exclude checks
require quotes around object literal property names (quote-props)
Object literal property names can be defined in two ways: using literals or using strings. For example, these two objects are equivalent:
var object1 = {
property: true
};
var object2 = {
"property": true
};
In many cases, it doesn't matter if you choose to use an identifier instead of a string or vice-versa. Even so, you might decide to enforce a consistent style in your code.
There are, however, some occasions when you must use quotes:
- If you are using an ECMAScript 3 JavaScript engine (such as IE8) and you want to use a keyword (such as
if
) as a property name. This restriction was removed in ECMAScript 5. - You want to use a non-identifier character in your property name, such as having a property with a space like
"one two"
.
Another example where quotes do matter is when using numeric literals as property keys:
var object = {
1e2: 1,
100: 2
};
This may look alright at first sight, but this code in fact throws a syntax error in ECMAScript 5 strict mode. This happens because 1e2
and 100
are coerced into strings before getting used as the property name. Both String(1e2)
and String(100)
happen to be equal to "100"
, which causes the "Duplicate data property in object literal not allowed in strict mode" error. Issues like that can be tricky to debug, so some prefer to require quotes around all property names.
Rule Details
This rule requires quotes around object literal property names.
Options
This rule has two options, a string option and an object option.
String option:
-
"always"
(default) requires quotes around all object literal property names -
"as-needed"
disallows quotes around object literal property names that are not strictly required -
"consistent"
enforces a consistent quote style requires quotes around object literal property names -
"consistent-as-needed"
requires quotes around all object literal property names if any name strictly requires quotes, otherwise disallows quotes around object property names
Object option:
-
"keywords": true
requires quotes around language keywords used as object property names (only applies when usingas-needed
orconsistent-as-needed
) -
"unnecessary": true
(default) disallows quotes around object literal property names that are not strictly required (only applies when usingas-needed
) -
"unnecessary": false
allows quotes around object literal property names that are not strictly required (only applies when usingas-needed
) -
"numbers": true
requires quotes around numbers used as object property names (only applies when usingas-needed
)
always
Examples of incorrect code for this rule with the default "always"
option:
/*eslint quote-props: ["error", "always"]*/
var object = {
foo: "bar",
baz: 42,
"qux-lorem": true
};
Examples of correct code for this rule with the default "always"
option:
/*eslint quote-props: ["error", "always"]*/
/*eslint-env es6*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42,
'qux-lorem': true
};
var object3 = {
foo() {
return;
}
};
as-needed
Examples of incorrect code for this rule with the "as-needed"
option:
/*eslint quote-props: ["error", "as-needed"]*/
var object = {
"a": 0,
"0": 0,
"true": 0,
"null": 0
};
Examples of correct code for this rule with the "as-needed"
option:
/*eslint quote-props: ["error", "as-needed"]*/
/*eslint-env es6*/
var object1 = {
"a-b": 0,
"0x0": 0,
"1e2": 0
};
var object2 = {
foo: 'bar',
baz: 42,
true: 0,
0: 0,
'qux-lorem': true
};
var object3 = {
foo() {
return;
}
};
consistent
Examples of incorrect code for this rule with the "consistent"
option:
/*eslint quote-props: ["error", "consistent"]*/
var object1 = {
foo: "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
baz: 42
};
Examples of correct code for this rule with the "consistent"
option:
/*eslint quote-props: ["error", "consistent"]*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42
};
var object3 = {
foo: 'bar',
baz: 42
};
consistent-as-needed
Examples of incorrect code for this rule with the "consistent-as-needed"
option:
/*eslint quote-props: ["error", "consistent-as-needed"]*/
var object1 = {
foo: "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42
};
Examples of correct code for this rule with the "consistent-as-needed"
option:
/*eslint quote-props: ["error", "consistent-as-needed"]*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
foo: 'bar',
baz: 42
};
keywords
Examples of additional incorrect code for this rule with the "as-needed", { "keywords": true }
options:
/*eslint quote-props: ["error", "as-needed", { "keywords": true }]*/
var x = {
while: 1,
volatile: "foo"
};
Examples of additional incorrect code for this rule with the "consistent-as-needed", { "keywords": true }
options:
/*eslint quote-props: ["error", "consistent-as-needed", { "keywords": true }]*/
var x = {
"prop": 1,
"bar": "foo"
};
unnecessary
Examples of additional correct code for this rule with the "as-needed", { "unnecessary": false }
options:
/*eslint quote-props: ["error", "as-needed", { "keywords": true, "unnecessary": false }]*/
var x = {
"while": 1,
"foo": "bar" // Would normally have caused a warning
};
numbers
Examples of additional incorrect code for this rule with the "as-needed", { "numbers": true }
options:
/*eslint quote-props: ["error", "as-needed", { "numbers": true }]*/
var x = {
100: 1
}
When Not To Use It
If you don't care if property names are consistently wrapped in quotes or not, and you don't target legacy ES3 environments, turn this rule off.
Further Reading
Properties shouldn't be quoted as all quotes are redundant. Open
"js": {
- Read upRead up
- Exclude checks
require quotes around object literal property names (quote-props)
Object literal property names can be defined in two ways: using literals or using strings. For example, these two objects are equivalent:
var object1 = {
property: true
};
var object2 = {
"property": true
};
In many cases, it doesn't matter if you choose to use an identifier instead of a string or vice-versa. Even so, you might decide to enforce a consistent style in your code.
There are, however, some occasions when you must use quotes:
- If you are using an ECMAScript 3 JavaScript engine (such as IE8) and you want to use a keyword (such as
if
) as a property name. This restriction was removed in ECMAScript 5. - You want to use a non-identifier character in your property name, such as having a property with a space like
"one two"
.
Another example where quotes do matter is when using numeric literals as property keys:
var object = {
1e2: 1,
100: 2
};
This may look alright at first sight, but this code in fact throws a syntax error in ECMAScript 5 strict mode. This happens because 1e2
and 100
are coerced into strings before getting used as the property name. Both String(1e2)
and String(100)
happen to be equal to "100"
, which causes the "Duplicate data property in object literal not allowed in strict mode" error. Issues like that can be tricky to debug, so some prefer to require quotes around all property names.
Rule Details
This rule requires quotes around object literal property names.
Options
This rule has two options, a string option and an object option.
String option:
-
"always"
(default) requires quotes around all object literal property names -
"as-needed"
disallows quotes around object literal property names that are not strictly required -
"consistent"
enforces a consistent quote style requires quotes around object literal property names -
"consistent-as-needed"
requires quotes around all object literal property names if any name strictly requires quotes, otherwise disallows quotes around object property names
Object option:
-
"keywords": true
requires quotes around language keywords used as object property names (only applies when usingas-needed
orconsistent-as-needed
) -
"unnecessary": true
(default) disallows quotes around object literal property names that are not strictly required (only applies when usingas-needed
) -
"unnecessary": false
allows quotes around object literal property names that are not strictly required (only applies when usingas-needed
) -
"numbers": true
requires quotes around numbers used as object property names (only applies when usingas-needed
)
always
Examples of incorrect code for this rule with the default "always"
option:
/*eslint quote-props: ["error", "always"]*/
var object = {
foo: "bar",
baz: 42,
"qux-lorem": true
};
Examples of correct code for this rule with the default "always"
option:
/*eslint quote-props: ["error", "always"]*/
/*eslint-env es6*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42,
'qux-lorem': true
};
var object3 = {
foo() {
return;
}
};
as-needed
Examples of incorrect code for this rule with the "as-needed"
option:
/*eslint quote-props: ["error", "as-needed"]*/
var object = {
"a": 0,
"0": 0,
"true": 0,
"null": 0
};
Examples of correct code for this rule with the "as-needed"
option:
/*eslint quote-props: ["error", "as-needed"]*/
/*eslint-env es6*/
var object1 = {
"a-b": 0,
"0x0": 0,
"1e2": 0
};
var object2 = {
foo: 'bar',
baz: 42,
true: 0,
0: 0,
'qux-lorem': true
};
var object3 = {
foo() {
return;
}
};
consistent
Examples of incorrect code for this rule with the "consistent"
option:
/*eslint quote-props: ["error", "consistent"]*/
var object1 = {
foo: "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
baz: 42
};
Examples of correct code for this rule with the "consistent"
option:
/*eslint quote-props: ["error", "consistent"]*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42
};
var object3 = {
foo: 'bar',
baz: 42
};
consistent-as-needed
Examples of incorrect code for this rule with the "consistent-as-needed"
option:
/*eslint quote-props: ["error", "consistent-as-needed"]*/
var object1 = {
foo: "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42
};
Examples of correct code for this rule with the "consistent-as-needed"
option:
/*eslint quote-props: ["error", "consistent-as-needed"]*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
foo: 'bar',
baz: 42
};
keywords
Examples of additional incorrect code for this rule with the "as-needed", { "keywords": true }
options:
/*eslint quote-props: ["error", "as-needed", { "keywords": true }]*/
var x = {
while: 1,
volatile: "foo"
};
Examples of additional incorrect code for this rule with the "consistent-as-needed", { "keywords": true }
options:
/*eslint quote-props: ["error", "consistent-as-needed", { "keywords": true }]*/
var x = {
"prop": 1,
"bar": "foo"
};
unnecessary
Examples of additional correct code for this rule with the "as-needed", { "unnecessary": false }
options:
/*eslint quote-props: ["error", "as-needed", { "keywords": true, "unnecessary": false }]*/
var x = {
"while": 1,
"foo": "bar" // Would normally have caused a warning
};
numbers
Examples of additional incorrect code for this rule with the "as-needed", { "numbers": true }
options:
/*eslint quote-props: ["error", "as-needed", { "numbers": true }]*/
var x = {
100: 1
}
When Not To Use It
If you don't care if property names are consistently wrapped in quotes or not, and you don't target legacy ES3 environments, turn this rule off.
Further Reading
'path' is assigned a value but never used. Open
path =require('path')
- 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/