case 0:

Close

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/

                this.emit('install_begin', target);

Close

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()) if thisArg 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/

                dirpath = void 0, sakuraname = void 0;

Close

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/

              case 22:

Close

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/

                _context11.next = 43;

Close

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

• JavaScript: Don’t Reassign Your Function Arguments Source: http://eslint.org/docs/rules/

                _context11.prev = 39;

Close

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

• JavaScript: Don’t Reassign Your Function Arguments Source: http://eslint.org/docs/rules/

     * load balloon

Close

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/

     * @type {cuttlebone}

Close

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/

     * @return {Promise}

Close

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/

                nanikaStorage = this.components.NanikaStorage;

Close

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()) if thisArg 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/

exports.NamedKernelManagerController = exports.NamedKernelManager = exports.NamedKernelManagerControllers = exports.NamedKernelManagerRoutings = undefined;

Close

Disallow Use of undefined Variable (no-undefined)

The undefined variable is unique in JavaScript because it is actually a property of the global object. As such, in ECMAScript 3 it was possible to overwrite the value of undefined. While ECMAScript 5 disallows overwriting undefined, it's still possible to shadow undefined, such as:

function doSomething(data) {
    var undefined = "hi";

    // doesn't do what you think it does
    if (data === undefined) {
        // ...
    }

}

This represents a problem for undefined that doesn't exist for null, which is a keyword and primitive value that can neither be overwritten nor shadowed.

All uninitialized variables automatically get the value of undefined:

var foo;

console.log(foo === undefined);     // true (assuming no shadowing)

For this reason, it's not necessary to explicitly initialize a variable to undefined.

Taking all of this into account, some style guides forbid the use of undefined, recommending instead:

• Variables that should be undefined are simply left uninitialized.
• Checking if a value is undefined should be done with typeof.
• Using the void operator to generate the value of undefined if necessary.

Rule Details

This rule aims to eliminate the use of undefined, and as such, generates a warning whenever it is used.

Examples of incorrect code for this rule:

/*eslint no-undefined: "error"*/

var foo = undefined;

var undefined = "foo";

if (foo === undefined) {
    // ...
}

function foo(undefined) {
    // ...
}

Examples of correct code for this rule:

/*eslint no-undefined: "error"*/

var foo = void 0;

var Undefined = "foo";

if (typeof foo === "undefined") {
    // ...
}

global.undefined = "foo";

When Not To Use It

If you want to allow the use of undefined in your code, then you can safely turn this rule off.

Further Reading

• undefined - JavaScript | MDN
• Understanding JavaScript’s ‘undefined’ | JavaScript, JavaScript...
• ECMA262 edition 5.1 §15.1.1.3: undefined

Related Rules

• [no-undef-init](no-undef-init.md)
• [no-void](no-void.md) Source: http://eslint.org/docs/rules/

                return NarLoader.loadFromURL(target);

Close

Disallow Undeclared Variables (no-undef)

This rule can help you locate potential ReferenceErrors resulting from misspellings of variable and parameter names, or accidental implicit globals (for example, from forgetting the var keyword in a for loop initializer).

Rule Details

Any reference to an undeclared variable causes a warning, unless the variable is explicitly mentioned in a /*global ...*/ comment.

Examples of incorrect code for this rule:

/*eslint no-undef: "error"*/

var a = someFunction();
b = 10;

Examples of correct code for this rule with global declaration:

/*global someFunction b:true*/
/*eslint no-undef: "error"*/

var a = someFunction();
b = 10;

The b:true syntax in /*global */ indicates that assignment to b is correct.

Examples of incorrect code for this rule with global declaration:

/*global b*/
/*eslint no-undef: "error"*/

b = 10;

By default, variables declared in /*global */ are read-only, therefore assignment is incorrect.

Options

• typeof set to true will warn for variables used inside typeof check (Default false).

typeof

Examples of correct code for the default { "typeof": false } option:

/*eslint no-undef: "error"*/

if (typeof UndefinedIdentifier === "undefined") {
    // do something ...
}

You can use this option if you want to prevent typeof check on a variable which has not been declared.

Examples of incorrect code for the { "typeof": true } option:

/*eslint no-undef: ["error", { "typeof": true }] */

if(typeof a === "string"){}

Examples of correct code for the { "typeof": true } option with global declaration:

/*global a*/
/*eslint no-undef: ["error", { "typeof": true }] */

if(typeof a === "string"){}

Environments

For convenience, ESLint provides shortcuts that pre-define global variables exposed by popular libraries and runtime environments. This rule supports these environments, as listed in Specifying Environments. A few examples are given below.

browser

Examples of correct code for this rule with browser environment:

/*eslint no-undef: "error"*/
/*eslint-env browser*/

setTimeout(function() {
    alert("Hello");
});

node

Examples of correct code for this rule with node environment:

/*eslint no-undef: "error"*/
/*eslint-env node*/

var fs = require("fs");
module.exports = function() {
    console.log(fs);
};

When Not To Use It

If explicit declaration of global variables is not to your taste.

Compatibility

This rule provides compatibility with treatment of global variables in JSHint and JSLint. Source: http://eslint.org/docs/rules/

                  _context11.next = 26;

Close

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

• JavaScript: Don’t Reassign Your Function Arguments Source: http://eslint.org/docs/rules/

var _keys2 = _interopRequireDefault(_keys);

Close

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

• JavaScript Scoping and Hoisting
• var Hoisting
• A criticism of the Single Var Pattern in JavaScript, and a simple alternative
• Multiple var statements in JavaScript, not superfluous Source: http://eslint.org/docs/rules/

     * ゴーストのビュークラス

Close

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/

    /**

Close

enforce valid JSDoc comments (valid-jsdoc)

JSDoc generates application programming interface (API) documentation from specially-formatted comments in JavaScript code. For example, this is a JSDoc comment for a function:

/**
 * Add two numbers.
 * @param {number} num1 The first number.
 * @param {number} num2 The second number.
 * @returns {number} The sum of the two numbers.
 */
function add(num1, num2) {
    return num1 + num2;
}

If comments are invalid because of typing mistakes, then documentation will be incomplete.

If comments are inconsistent because they are not updated when function definitions are modified, then readers might become confused.

Rule Details

This rule enforces valid and consistent JSDoc comments. It reports any of the following problems:

• missing parameter tag: @arg, @argument, or @param
• inconsistent order of parameter names in a comment compared to the function or method
• missing return tag: @return or @returns
• missing parameter or return type
• missing parameter or return description
• syntax error

This rule does not report missing JSDoc comments for classes, functions, or methods.

Note: This rule does not support all of the Google Closure documentation tool's use cases. As such, some code such as (/**number*/ n => n * 2); will be flagged as missing appropriate function JSDoc comments even though /**number*/ is intended to be a type hint and not a documentation block for the function. We don't recommend using this rule if you use type hints in this way.

Examples of incorrect code for this rule:

/*eslint valid-jsdoc: "error"*/

// expected @param tag for parameter num1 but found num instead
// missing @param tag for parameter num2
// missing return type
/**
 * Add two numbers.
 * @param {number} num The first number.
 * @returns The sum of the two numbers.
 */
function add(num1, num2) {
    return num1 + num2;
}

// missing brace
// missing @returns tag
/**
 * @param {string name Whom to greet.
 */
function greet(name) {
    console.log("Hello " + name);
}

// missing parameter type for num1
// missing parameter description for num2
/**
 * Represents a sum.
 * @constructor
 * @param num1 The first number.
 * @param {number} num2
 */
function sum(num1, num2) {
    this.num1 = num1;
    this.num2 = num2;
}

Examples of correct code for this rule:

/*eslint valid-jsdoc: "error"*/
/*eslint-env es6*/

/**
 * Add two numbers.
 * @param {number} num1 The first number.
 * @param {number} num2 The second number.
 * @returns {number} The sum of the two numbers.
 */
function add(num1, num2) {
    return num1 + num2;
}

// default options allow missing function description
// return type `void` means the function has no `return` statement
/**
 * @param {string} name Whom to greet.
 * @returns {void}
 */
function greet(name) {
    console.log("Hello " + name);
}

// @constructor tag allows missing @returns tag
/**
 * Represents a sum.
 * @constructor
 * @param {number} num1 The first number.
 * @param {number} num2 The second number.
 */
function sum(num1, num2) {
    this.num1 = num1;
    this.num2 = num2;
}

// class constructor allows missing @returns tag
/**
 * Represents a sum.
 */
class Sum {
    /**
     * @param {number} num1 The first number.
     * @param {number} num2 The second number.
     */
    constructor(num1, num2) {
        this.num1 = num1;
        this.num2 = num2;
    }
}

// @abstract tag allows @returns tag without `return` statement
class Widget {
    /**
    * When the state changes, does it affect the rendered appearance?
    * @abstract
    * @param {Object} state The new state of the widget.
    * @returns {boolean} Is current appearance inconsistent with new state?
    */
    mustRender (state) {
        throw new Error("Widget subclass did not implement mustRender");
    }
}

// @override tag allows missing @param and @returns tags
class WonderfulWidget extends Widget {
    /**
     * @override
     */
    mustRender (state) {
        return state !== this.state; // shallow comparison
    }
}

Options

This rule has an object option:

• "prefer" enforces consistent documentation tags specified by an object whose properties mean instead of key use value (for example, "return": "returns" means instead of @return use @returns)
• "preferType" enforces consistent type strings specified by an object whose properties mean instead of key use value (for example, "object": "Object" means instead of object use Object)
• "requireReturn" requires a return tag:
  • true (default) even if the function or method does not have a return statement (this option value does not apply to constructors)
  • false if and only if the function or method has a return statement (this option value does apply to constructors)
• "requireReturnType": false allows missing type in return tags
• "matchDescription" specifies (as a string) a regular expression to match the description in each JSDoc comment (for example, ".+" requires a description; this option does not apply to descriptions in parameter or return tags)
• "requireParamDescription": false allows missing description in parameter tags
• "requireReturnDescription": false allows missing description in return tags

prefer

Examples of additional incorrect code for this rule with sample "prefer": { "arg": "param", "argument": "param", "class": "constructor", "return": "returns", "virtual": "abstract" } options:

/*eslint valid-jsdoc: ["error", { "prefer": { "arg": "param", "argument": "param", "class": "constructor", "return": "returns", "virtual": "abstract" } }]*/
/*eslint-env es6*/

/**
 * Add two numbers.
 * @arg {int} num1 The first number.
 * @arg {int} num2 The second number.
 * @return {int} The sum of the two numbers.
 */
function add(num1, num2) {
    return num1 + num2;
}

/**
 * Represents a sum.
 * @class
 * @argument {number} num1 The first number.
 * @argument {number} num2 The second number.
 */
function sum(num1, num2) {
    this.num1 = num1;
    this.num2 = num2;
}

class Widget {
    /**
     * When the state changes, does it affect the rendered appearance?
     * @virtual
     * @argument {Object} state The new state of the widget.
     * @return {boolean} Is current appearance inconsistent with new state?
     */
    mustRender (state) {
        throw new Error("Widget subclass did not implement mustRender");
    }
}

preferType

Examples of additional incorrect code for this rule with sample "preferType": { "Boolean": "boolean", "Number": "number", "object": "Object", "String": "string" } options:

/*eslint valid-jsdoc: ["error", { "preferType": { "Boolean": "boolean", "Number": "number", "object": "Object", "String": "string" } }]*/
/*eslint-env es6*/

/**
 * Add two numbers.
 * @param {Number} num1 The first number.
 * @param {Number} num2 The second number.
 * @returns {Number} The sum of the two numbers.
 */
function add(num1, num2) {
    return num1 + num2;
}

/**
 * Output a greeting as a side effect.
 * @param {String} name Whom to greet.
 * @returns {void}
 */
function greet(name) {
    console.log("Hello " + name);
}

class Widget {
    /**
     * When the state changes, does it affect the rendered appearance?
     * @abstract
     * @param {object} state The new state of the widget.
     * @returns {Boolean} Is current appearance inconsistent with new state?
     */
    mustRender (state) {
        throw new Error("Widget subclass did not implement mustRender");
    }
}

requireReturn

Examples of additional incorrect code for this rule with the "requireReturn": false option:

/*eslint valid-jsdoc: ["error", { "requireReturn": false }]*/

// unexpected @returns tag because function has no `return` statement
/**
 * @param {string} name Whom to greet.
 * @returns {string} The greeting.
 */
function greet(name) {
    console.log("Hello " + name);
}

// add @abstract tag to allow @returns tag without `return` statement
class Widget {
    /**
     * When the state changes, does it affect the rendered appearance?
     * @param {Object} state The new state of the widget.
     * @returns {boolean} Is current appearance inconsistent with new state?
     */
    mustRender (state) {
        throw new Error("Widget subclass did not implement mustRender");
    }
}

Example of additional correct code for this rule with the "requireReturn": false option:

/*eslint valid-jsdoc: ["error", { "requireReturn": false }]*/

/**
 * @param {string} name Whom to greet.
 */
function greet(name) {
    console.log("Hello " + name);
}

requireReturnType

Example of additional correct code for this rule with the "requireReturnType": false option:

/*eslint valid-jsdoc: ["error", { "requireReturnType": false }]*/

/**
 * Add two numbers.
 * @param {number} num1 The first number.
 * @param {number} num2 The second number.
 * @returns The sum of the two numbers.
 */
function add(num1, num2) {
    return num1 + num2;
}

matchDescription

Example of additional incorrect code for this rule with a sample "matchDescription": ".+" option:

/*eslint valid-jsdoc: ["error", { "matchDescription": ".+" }]*/

// missing function description
/**
 * @param {string} name Whom to greet.
 * @returns {void}
 */
function greet(name) {
    console.log("Hello " + name);
}

requireParamDescription

Example of additional correct code for this rule with the "requireParamDescription": false option:

/*eslint valid-jsdoc: ["error", { "requireParamDescription": false }]*/

/**
 * Add two numbers.
 * @param {int} num1
 * @param {int} num2
 * @returns {int} The sum of the two numbers.
 */
function add(num1, num2) {
    return num1 + num2;
}

requireReturnDescription

Example of additional correct code for this rule with the "requireReturnDescription": false option:

/*eslint valid-jsdoc: ["error", { "requireReturnDescription": false }]*/

/**
 * Add two numbers.
 * @param {number} num1 The first number.
 * @param {number} num2 The second number.
 * @returns {number}
 */
function add(num1, num2) {
    return num1 + num2;
}

When Not To Use It

If you aren't using JSDoc, then you can safely turn this rule off.

Further Reading

• JSDoc

Related Rules

• [require-jsdoc](require-jsdoc.md) Source: http://eslint.org/docs/rules/

    /**

Close

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/

Object.defineProperty(exports, "__esModule", {

Close

enforce the consistent use of either backticks, double, or single quotes (quotes)

JavaScript allows you to define strings in one of three ways: double quotes, single quotes, and backticks (as of ECMAScript 6). For example:

/*eslint-env es6*/

var double = "double";
var single = 'single';
var backtick = `backtick`;    // ES6 only

Each of these lines creates a string and, in some cases, can be used interchangeably. The choice of how to define strings in a codebase is a stylistic one outside of template literals (which allow embedded of expressions to be interpreted).

Many codebases require strings to be defined in a consistent manner.

Rule Details

This rule enforces the consistent use of either backticks, double, or single quotes.

Options

This rule has two options, a string option and an object option.

String option:

• "double" (default) requires the use of double quotes wherever possible
• "single" requires the use of single quotes wherever possible
• "backtick" requires the use of backticks wherever possible

Object option:

• "avoidEscape": true allows strings to use single-quotes or double-quotes so long as the string contains a quote that would have to be escaped otherwise
• "allowTemplateLiterals": true allows strings to use backticks

Deprecated: The object property avoid-escape is deprecated; please use the object property avoidEscape instead.

double

Examples of incorrect code for this rule with the default "double" option:

/*eslint quotes: ["error", "double"]*/

var single = 'single';
var unescaped = 'a string containing "double" quotes';

Examples of correct code for this rule with the default "double" option:

/*eslint quotes: ["error", "double"]*/
/*eslint-env es6*/

var double = "double";
var backtick = `back\ntick`;  // backticks are allowed due to newline
var backtick = tag`backtick`; // backticks are allowed due to tag

single

Examples of incorrect code for this rule with the "single" option:

/*eslint quotes: ["error", "single"]*/

var double = "double";
var unescaped = "a string containing 'single' quotes";

Examples of correct code for this rule with the "single" option:

/*eslint quotes: ["error", "single"]*/
/*eslint-env es6*/

var single = 'single';
var backtick = `back${x}tick`; // backticks are allowed due to substitution

backticks

Examples of incorrect code for this rule with the "backtick" option:

/*eslint quotes: ["error", "backtick"]*/

var single = 'single';
var double = "double";
var unescaped = 'a string containing `backticks`';

Examples of correct code for this rule with the "backtick" option:

/*eslint quotes: ["error", "backtick"]*/
/*eslint-env es6*/

var backtick = `backtick`;

avoidEscape

Examples of additional correct code for this rule with the "double", { "avoidEscape": true } options:

/*eslint quotes: ["error", "double", { "avoidEscape": true }]*/

var single = 'a string containing "double" quotes';

Examples of additional correct code for this rule with the "single", { "avoidEscape": true } options:

/*eslint quotes: ["error", "single", { "avoidEscape": true }]*/

var double = "a string containing 'single' quotes";

Examples of additional correct code for this rule with the "backtick", { "avoidEscape": true } options:

/*eslint quotes: ["error", "backtick", { "avoidEscape": true }]*/

var double = "a string containing `backtick` quotes"

allowTemplateLiterals

Examples of additional correct code for this rule with the "double", { "allowTemplateLiterals": true } options:

/*eslint quotes: ["error", "double", { "allowTemplateLiterals": true }]*/

var double = "double";
var double = `double`;

Examples of additional correct code for this rule with the "single", { "allowTemplateLiterals": true } options:

/*eslint quotes: ["error", "single", { "allowTemplateLiterals": true }]*/

var single = 'single';
var single = `single`;

When Not To Use It

If you do not need consistency in your string styles, you can safely disable this rule. Source: http://eslint.org/docs/rules/

              case 2:

Close

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/

        var from = arguments.length <= 1 || arguments[1] === undefined ? null : arguments[1];

Close

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/