Showing 2,519 of 2,519 total issues
Unnecessary semicolon. Open
;
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- Exclude checks
disallow unnecessary semicolons (no-extra-semi)
Typing mistakes and misunderstandings about where semicolons are required can lead to semicolons that are unnecessary. While not technically an error, extra semicolons can cause confusion when reading code.
Rule Details
This rule disallows unnecessary semicolons.
Examples of incorrect code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;;
function foo() {
// code
};
Examples of correct code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;
var foo = function() {
// code
};
When Not To Use It
If you intentionally use extra semicolons then you can disable this rule.
Related Rules
- [semi](semi.md)
- [semi-spacing](semi-spacing.md) Source: http://eslint.org/docs/rules/
Unnecessary semicolon. Open
;__weex_define__("@weex-component/wxc-marquee", [], function(__weex_require__, __weex_exports__, __weex_module__){
- Read upRead up
- Exclude checks
disallow unnecessary semicolons (no-extra-semi)
Typing mistakes and misunderstandings about where semicolons are required can lead to semicolons that are unnecessary. While not technically an error, extra semicolons can cause confusion when reading code.
Rule Details
This rule disallows unnecessary semicolons.
Examples of incorrect code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;;
function foo() {
// code
};
Examples of correct code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;
var foo = function() {
// code
};
When Not To Use It
If you intentionally use extra semicolons then you can disable this rule.
Related Rules
- [semi](semi.md)
- [semi-spacing](semi-spacing.md) Source: http://eslint.org/docs/rules/
Unexpected 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/
Unexpected trailing comma. Open
backgroundColor: '#ffffff',
- 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/
Unexpected 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/
The body of a for-in should be wrapped in an if statement to filter unwanted properties from the prototype. Open
for (var i in this.items) {
- Read upRead up
- Exclude checks
Require Guarding for-in (guard-for-in)
Looping over objects with a for in
loop will include properties that are inherited through the prototype chain. This behavior can lead to unexpected items in your for loop.
for (key in foo) {
doSomething(key);
}
Note that simply checking foo.hasOwnProperty(key)
is likely to cause an error in some cases; see [no-prototype-builtins](no-prototype-builtins.md).
Rule Details
This rule is aimed at preventing unexpected behavior that could arise from using a for in
loop without filtering the results in the loop. As such, it will warn when for in
loops do not filter their results with an if
statement.
Examples of incorrect code for this rule:
/*eslint guard-for-in: "error"*/
for (key in foo) {
doSomething(key);
}
Examples of correct code for this rule:
/*eslint guard-for-in: "error"*/
for (key in foo) {
if (Object.prototype.hasOwnProperty.call(foo, key)) {
doSomething(key);
}
if ({}.hasOwnProperty.call(foo, key)) {
doSomething(key);
}
}
Related Rules
- [no-prototype-builtins](no-prototype-builtins.md)
Further Reading
Move the invocation into the parens that contain the function. Open
/******/ (function(modules) { // webpackBootstrap
- Read upRead up
- Exclude checks
Require IIFEs to be Wrapped (wrap-iife)
You can immediately invoke function expressions, but not function declarations. A common technique to create an immediately-invoked function expression (IIFE) is to wrap a function declaration in parentheses. The opening parentheses causes the contained function to be parsed as an expression, rather than a declaration.
// function expression could be unwrapped
var x = function () { return { y: 1 };}();
// function declaration must be wrapped
function () { /* side effects */ }(); // SyntaxError
Rule Details
This rule requires all immediately-invoked function expressions to be wrapped in parentheses.
Options
This rule has two options, a string option and an object option.
String option:
-
"outside"
enforces always wrapping the call expression. The default is"outside"
. -
"inside"
enforces always wrapping the function expression. -
"any"
enforces always wrapping, but allows either style.
Object option:
-
"functionPrototypeMethods": true
additionally enforces wrapping function expressions invoked using.call
and.apply
. The default isfalse
.
outside
Examples of incorrect code for the default "outside"
option:
/*eslint wrap-iife: ["error", "outside"]*/
var x = function () { return { y: 1 };}(); // unwrapped
var x = (function () { return { y: 1 };})(); // wrapped function expression
Examples of correct code for the default "outside"
option:
/*eslint wrap-iife: ["error", "outside"]*/
var x = (function () { return { y: 1 };}()); // wrapped call expression
inside
Examples of incorrect code for the "inside"
option:
/*eslint wrap-iife: ["error", "inside"]*/
var x = function () { return { y: 1 };}(); // unwrapped
var x = (function () { return { y: 1 };}()); // wrapped call expression
Examples of correct code for the "inside"
option:
/*eslint wrap-iife: ["error", "inside"]*/
var x = (function () { return { y: 1 };})(); // wrapped function expression
any
Examples of incorrect code for the "any"
option:
/*eslint wrap-iife: ["error", "any"]*/
var x = function () { return { y: 1 };}(); // unwrapped
Examples of correct code for the "any"
option:
/*eslint wrap-iife: ["error", "any"]*/
var x = (function () { return { y: 1 };}()); // wrapped call expression
var x = (function () { return { y: 1 };})(); // wrapped function expression
functionPrototypeMethods
Examples of incorrect code for this rule with the "inside", { "functionPrototypeMethods": true }
options:
/* eslint wrap-iife: [2, "inside", { functionPrototypeMethods: true }] */
var x = function(){ foo(); }()
var x = (function(){ foo(); }())
var x = function(){ foo(); }.call(bar)
var x = (function(){ foo(); }.call(bar))
Examples of correct code for this rule with the "inside", { "functionPrototypeMethods": true }
options:
/* eslint wrap-iife: [2, "inside", { functionPrototypeMethods: true }] */
var x = (function(){ foo(); })()
var x = (function(){ foo(); }).call(bar)
Source: http://eslint.org/docs/rules/
Move the invocation into the parens that contain the function. Open
/******/ (function(modules) { // webpackBootstrap
- Read upRead up
- Exclude checks
Require IIFEs to be Wrapped (wrap-iife)
You can immediately invoke function expressions, but not function declarations. A common technique to create an immediately-invoked function expression (IIFE) is to wrap a function declaration in parentheses. The opening parentheses causes the contained function to be parsed as an expression, rather than a declaration.
// function expression could be unwrapped
var x = function () { return { y: 1 };}();
// function declaration must be wrapped
function () { /* side effects */ }(); // SyntaxError
Rule Details
This rule requires all immediately-invoked function expressions to be wrapped in parentheses.
Options
This rule has two options, a string option and an object option.
String option:
-
"outside"
enforces always wrapping the call expression. The default is"outside"
. -
"inside"
enforces always wrapping the function expression. -
"any"
enforces always wrapping, but allows either style.
Object option:
-
"functionPrototypeMethods": true
additionally enforces wrapping function expressions invoked using.call
and.apply
. The default isfalse
.
outside
Examples of incorrect code for the default "outside"
option:
/*eslint wrap-iife: ["error", "outside"]*/
var x = function () { return { y: 1 };}(); // unwrapped
var x = (function () { return { y: 1 };})(); // wrapped function expression
Examples of correct code for the default "outside"
option:
/*eslint wrap-iife: ["error", "outside"]*/
var x = (function () { return { y: 1 };}()); // wrapped call expression
inside
Examples of incorrect code for the "inside"
option:
/*eslint wrap-iife: ["error", "inside"]*/
var x = function () { return { y: 1 };}(); // unwrapped
var x = (function () { return { y: 1 };}()); // wrapped call expression
Examples of correct code for the "inside"
option:
/*eslint wrap-iife: ["error", "inside"]*/
var x = (function () { return { y: 1 };})(); // wrapped function expression
any
Examples of incorrect code for the "any"
option:
/*eslint wrap-iife: ["error", "any"]*/
var x = function () { return { y: 1 };}(); // unwrapped
Examples of correct code for the "any"
option:
/*eslint wrap-iife: ["error", "any"]*/
var x = (function () { return { y: 1 };}()); // wrapped call expression
var x = (function () { return { y: 1 };})(); // wrapped function expression
functionPrototypeMethods
Examples of incorrect code for this rule with the "inside", { "functionPrototypeMethods": true }
options:
/* eslint wrap-iife: [2, "inside", { functionPrototypeMethods: true }] */
var x = function(){ foo(); }()
var x = (function(){ foo(); }())
var x = function(){ foo(); }.call(bar)
var x = (function(){ foo(); }.call(bar))
Examples of correct code for this rule with the "inside", { "functionPrototypeMethods": true }
options:
/* eslint wrap-iife: [2, "inside", { functionPrototypeMethods: true }] */
var x = (function(){ foo(); })()
var x = (function(){ foo(); }).call(bar)
Source: http://eslint.org/docs/rules/
Move the invocation into the parens that contain the function. Open
/******/ (function(modules) { // webpackBootstrap
- Read upRead up
- Exclude checks
Require IIFEs to be Wrapped (wrap-iife)
You can immediately invoke function expressions, but not function declarations. A common technique to create an immediately-invoked function expression (IIFE) is to wrap a function declaration in parentheses. The opening parentheses causes the contained function to be parsed as an expression, rather than a declaration.
// function expression could be unwrapped
var x = function () { return { y: 1 };}();
// function declaration must be wrapped
function () { /* side effects */ }(); // SyntaxError
Rule Details
This rule requires all immediately-invoked function expressions to be wrapped in parentheses.
Options
This rule has two options, a string option and an object option.
String option:
-
"outside"
enforces always wrapping the call expression. The default is"outside"
. -
"inside"
enforces always wrapping the function expression. -
"any"
enforces always wrapping, but allows either style.
Object option:
-
"functionPrototypeMethods": true
additionally enforces wrapping function expressions invoked using.call
and.apply
. The default isfalse
.
outside
Examples of incorrect code for the default "outside"
option:
/*eslint wrap-iife: ["error", "outside"]*/
var x = function () { return { y: 1 };}(); // unwrapped
var x = (function () { return { y: 1 };})(); // wrapped function expression
Examples of correct code for the default "outside"
option:
/*eslint wrap-iife: ["error", "outside"]*/
var x = (function () { return { y: 1 };}()); // wrapped call expression
inside
Examples of incorrect code for the "inside"
option:
/*eslint wrap-iife: ["error", "inside"]*/
var x = function () { return { y: 1 };}(); // unwrapped
var x = (function () { return { y: 1 };}()); // wrapped call expression
Examples of correct code for the "inside"
option:
/*eslint wrap-iife: ["error", "inside"]*/
var x = (function () { return { y: 1 };})(); // wrapped function expression
any
Examples of incorrect code for the "any"
option:
/*eslint wrap-iife: ["error", "any"]*/
var x = function () { return { y: 1 };}(); // unwrapped
Examples of correct code for the "any"
option:
/*eslint wrap-iife: ["error", "any"]*/
var x = (function () { return { y: 1 };}()); // wrapped call expression
var x = (function () { return { y: 1 };})(); // wrapped function expression
functionPrototypeMethods
Examples of incorrect code for this rule with the "inside", { "functionPrototypeMethods": true }
options:
/* eslint wrap-iife: [2, "inside", { functionPrototypeMethods: true }] */
var x = function(){ foo(); }()
var x = (function(){ foo(); }())
var x = function(){ foo(); }.call(bar)
var x = (function(){ foo(); }.call(bar))
Examples of correct code for this rule with the "inside", { "functionPrototypeMethods": true }
options:
/* eslint wrap-iife: [2, "inside", { functionPrototypeMethods: true }] */
var x = (function(){ foo(); })()
var x = (function(){ foo(); }).call(bar)
Source: http://eslint.org/docs/rules/
Unexpected newline between function and ( of function call. Open
/******/ ([
- Read upRead up
- Exclude checks
disallow confusing multiline expressions (no-unexpected-multiline)
Semicolons are usually optional in JavaScript, because of automatic semicolon insertion (ASI). You can require or disallow semicolons with the [semi](./semi.md) rule.
The rules for ASI are relatively straightforward: As once described by Isaac Schlueter, a newline character always ends a statement, just like a semicolon, except where one of the following is true:
- The statement has an unclosed paren, array literal, or object literal or ends in some other way that is not a valid way to end a statement. (For instance, ending with
.
or,
.) - The line is
--
or++
(in which case it will decrement/increment the next token.) - It is a
for()
,while()
,do
,if()
, orelse
, and there is no{
- The next line starts with
[
,(
,+
,*
,/
,-
,,
,.
, or some other binary operator that can only be found between two tokens in a single expression.
In the exceptions where a newline does not end a statement, a typing mistake to omit a semicolon causes two unrelated consecutive lines to be interpreted as one expression. Especially for a coding style without semicolons, readers might overlook the mistake. Although syntactically correct, the code might throw exceptions when it is executed.
Rule Details
This rule disallows confusing multiline expressions where a newline looks like it is ending a statement, but is not.
Examples of incorrect code for this rule:
/*eslint no-unexpected-multiline: "error"*/
var foo = bar
(1 || 2).baz();
var hello = 'world'
[1, 2, 3].forEach(addNumber);
let x = function() {}
`hello`
let x = function() {}
x
`hello`
Examples of correct code for this rule:
/*eslint no-unexpected-multiline: "error"*/
var foo = bar;
(1 || 2).baz();
var foo = bar
;(1 || 2).baz()
var hello = 'world';
[1, 2, 3].forEach(addNumber);
var hello = 'world'
void [1, 2, 3].forEach(addNumber);
let x = function() {};
`hello`
let tag = function() {}
tag `hello`
When Not To Use It
You can turn this rule off if you are confident that you will not accidentally introduce code like this.
Note that the patterns considered problems are not flagged by the [semi](semi.md) rule.
Related Rules
- [func-call-spacing](func-call-spacing.md)
- [semi](semi.md)
- [space-unary-ops](space-unary-ops.md) Source: http://eslint.org/docs/rules/
Unnecessary semicolon. Open
;
- Read upRead up
- Exclude checks
disallow unnecessary semicolons (no-extra-semi)
Typing mistakes and misunderstandings about where semicolons are required can lead to semicolons that are unnecessary. While not technically an error, extra semicolons can cause confusion when reading code.
Rule Details
This rule disallows unnecessary semicolons.
Examples of incorrect code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;;
function foo() {
// code
};
Examples of correct code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;
var foo = function() {
// code
};
When Not To Use It
If you intentionally use extra semicolons then you can disable this rule.
Related Rules
- [semi](semi.md)
- [semi-spacing](semi-spacing.md) Source: http://eslint.org/docs/rules/
Unnecessary semicolon. Open
;__weex_define__("@weex-component/wxc-tabitem", [], function(__weex_require__, __weex_exports__, __weex_module__){
- Read upRead up
- Exclude checks
disallow unnecessary semicolons (no-extra-semi)
Typing mistakes and misunderstandings about where semicolons are required can lead to semicolons that are unnecessary. While not technically an error, extra semicolons can cause confusion when reading code.
Rule Details
This rule disallows unnecessary semicolons.
Examples of incorrect code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;;
function foo() {
// code
};
Examples of correct code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;
var foo = function() {
// code
};
When Not To Use It
If you intentionally use extra semicolons then you can disable this rule.
Related Rules
- [semi](semi.md)
- [semi-spacing](semi-spacing.md) Source: http://eslint.org/docs/rules/
Unnecessary semicolon. Open
;__weex_define__("@weex-component/8e6cff2d0487efb24411ddaeb27766c3", [], function(__weex_require__, __weex_exports__, __weex_module__){
- Read upRead up
- Exclude checks
disallow unnecessary semicolons (no-extra-semi)
Typing mistakes and misunderstandings about where semicolons are required can lead to semicolons that are unnecessary. While not technically an error, extra semicolons can cause confusion when reading code.
Rule Details
This rule disallows unnecessary semicolons.
Examples of incorrect code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;;
function foo() {
// code
};
Examples of correct code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;
var foo = function() {
// code
};
When Not To Use It
If you intentionally use extra semicolons then you can disable this rule.
Related Rules
- [semi](semi.md)
- [semi-spacing](semi-spacing.md) Source: http://eslint.org/docs/rules/
Unnecessary semicolon. Open
;
- Read upRead up
- Exclude checks
disallow unnecessary semicolons (no-extra-semi)
Typing mistakes and misunderstandings about where semicolons are required can lead to semicolons that are unnecessary. While not technically an error, extra semicolons can cause confusion when reading code.
Rule Details
This rule disallows unnecessary semicolons.
Examples of incorrect code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;;
function foo() {
// code
};
Examples of correct code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;
var foo = function() {
// code
};
When Not To Use It
If you intentionally use extra semicolons then you can disable this rule.
Related Rules
- [semi](semi.md)
- [semi-spacing](semi-spacing.md) Source: http://eslint.org/docs/rules/
Unnecessary semicolon. Open
;
- Read upRead up
- Exclude checks
disallow unnecessary semicolons (no-extra-semi)
Typing mistakes and misunderstandings about where semicolons are required can lead to semicolons that are unnecessary. While not technically an error, extra semicolons can cause confusion when reading code.
Rule Details
This rule disallows unnecessary semicolons.
Examples of incorrect code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;;
function foo() {
// code
};
Examples of correct code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;
var foo = function() {
// code
};
When Not To Use It
If you intentionally use extra semicolons then you can disable this rule.
Related Rules
- [semi](semi.md)
- [semi-spacing](semi-spacing.md) Source: http://eslint.org/docs/rules/
Unnecessary semicolon. Open
;__weex_define__("@weex-component/wxc-countdown", [], function(__weex_require__, __weex_exports__, __weex_module__){
- Read upRead up
- Exclude checks
disallow unnecessary semicolons (no-extra-semi)
Typing mistakes and misunderstandings about where semicolons are required can lead to semicolons that are unnecessary. While not technically an error, extra semicolons can cause confusion when reading code.
Rule Details
This rule disallows unnecessary semicolons.
Examples of incorrect code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;;
function foo() {
// code
};
Examples of correct code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;
var foo = function() {
// code
};
When Not To Use It
If you intentionally use extra semicolons then you can disable this rule.
Related Rules
- [semi](semi.md)
- [semi-spacing](semi-spacing.md) Source: http://eslint.org/docs/rules/
Missing radix parameter. Open
this.time.H = String(parseInt(remain / 3600));
- Read upRead up
- Exclude checks
Require Radix Parameter (radix)
When using the parseInt()
function it is common to omit the second argument, the radix, and let the function try to determine from the first argument what type of number it is. By default, parseInt()
will autodetect decimal and hexadecimal (via 0x
prefix). Prior to ECMAScript 5, parseInt()
also autodetected octal literals, which caused problems because many developers assumed a leading 0
would be ignored.
This confusion led to the suggestion that you always use the radix parameter to parseInt()
to eliminate unintended consequences. So instead of doing this:
var num = parseInt("071"); // 57
Do this:
var num = parseInt("071", 10); // 71
ECMAScript 5 changed the behavior of parseInt()
so that it no longer autodetects octal literals and instead treats them as decimal literals. However, the differences between hexadecimal and decimal interpretation of the first parameter causes many developers to continue using the radix parameter to ensure the string is interpreted in the intended way.
On the other hand, if the code is targeting only ES5-compliant environments passing the radix 10
may be redundant. In such a case you might want to disallow using such a radix.
Rule Details
This rule is aimed at preventing the unintended conversion of a string to a number of a different base than intended or at preventing the redundant 10
radix if targeting modern environments only.
Options
There are two options for this rule:
-
"always"
enforces providing a radix (default) -
"as-needed"
disallows providing the10
radix
always
Examples of incorrect code for the default "always"
option:
/*eslint radix: "error"*/
var num = parseInt("071");
var num = parseInt(someValue);
var num = parseInt("071", "abc");
var num = parseInt();
Examples of correct code for the default "always"
option:
/*eslint radix: "error"*/
var num = parseInt("071", 10);
var num = parseInt("071", 8);
var num = parseFloat(someValue);
as-needed
Examples of incorrect code for the "as-needed"
option:
/*eslint radix: ["error", "as-needed"]*/
var num = parseInt("071", 10);
var num = parseInt("071", "abc");
var num = parseInt();
Examples of correct code for the "as-needed"
option:
/*eslint radix: ["error", "as-needed"]*/
var num = parseInt("071");
var num = parseInt("071", 8);
var num = parseFloat(someValue);
When Not To Use It
If you don't want to enforce either presence or omission of the 10
radix value you can turn this rule off.
Further Reading
Unnecessary semicolon. Open
;__weex_module__.exports.template = __weex_module__.exports.template || {}
- Read upRead up
- Exclude checks
disallow unnecessary semicolons (no-extra-semi)
Typing mistakes and misunderstandings about where semicolons are required can lead to semicolons that are unnecessary. While not technically an error, extra semicolons can cause confusion when reading code.
Rule Details
This rule disallows unnecessary semicolons.
Examples of incorrect code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;;
function foo() {
// code
};
Examples of correct code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;
var foo = function() {
// code
};
When Not To Use It
If you intentionally use extra semicolons then you can disable this rule.
Related Rules
- [semi](semi.md)
- [semi-spacing](semi-spacing.md) Source: http://eslint.org/docs/rules/
Unnecessary semicolon. Open
;__weex_define__("@weex-component/wxc-tabitem", [], function(__weex_require__, __weex_exports__, __weex_module__){
- Read upRead up
- Exclude checks
disallow unnecessary semicolons (no-extra-semi)
Typing mistakes and misunderstandings about where semicolons are required can lead to semicolons that are unnecessary. While not technically an error, extra semicolons can cause confusion when reading code.
Rule Details
This rule disallows unnecessary semicolons.
Examples of incorrect code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;;
function foo() {
// code
};
Examples of correct code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;
var foo = function() {
// code
};
When Not To Use It
If you intentionally use extra semicolons then you can disable this rule.
Related Rules
- [semi](semi.md)
- [semi-spacing](semi-spacing.md) Source: http://eslint.org/docs/rules/