// jogwheel does not support asynchronously running animations

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enforce or disallow capitalization of the first letter of a comment (capitalized-comments)

Comments are useful for leaving information for future developers. In order for that information to be useful and not distracting, it is sometimes desirable for comments to follow a particular style. One element of comment formatting styles is whether the first word of a comment should be capitalized or lowercase.

In general, no comment style is any more or less valid than any others, but many developers would agree that a consistent style can improve a project's maintainability.

Rule Details

This rule aims to enforce a consistent style of comments across your codebase, specifically by either requiring or disallowing a capitalized letter as the first word character in a comment. This rule will not issue warnings when non-cased letters are used.

By default, this rule will require a non-lowercase letter at the beginning of comments.

Examples of incorrect code for this rule:

/* eslint capitalized-comments: ["error"] */

// lowercase comment

Examples of correct code for this rule:

// Capitalized comment

// 1. Non-letter at beginning of comment

// 丈 Non-Latin character at beginning of comment

/* eslint semi:off */
/* eslint-env node */
/* eslint-disable */
/* eslint-enable */
/* istanbul ignore next */
/* jscs:enable */
/* jshint asi:true */
/* global foo */
/* globals foo */
/* exported myVar */
// eslint-disable-line
// eslint-disable-next-line
// https://github.com

Options

This rule has two options: a string value "always" or "never" which determines whether capitalization of the first word of a comment should be required or forbidden, and optionally an object containing more configuration parameters for the rule.

Here are the supported object options:

• ignorePattern: A string representing a regular expression pattern of words that should be ignored by this rule. If the first word of a comment matches the pattern, this rule will not report that comment.
  • Note that the following words are always ignored by this rule: ["jscs", "jshint", "eslint", "istanbul", "global", "globals", "exported"].
• ignoreInlineComments: If this is true, the rule will not report on comments in the middle of code. By default, this is false.
• ignoreConsecutiveComments: If this is true, the rule will not report on a comment which violates the rule, as long as the comment immediately follows another comment. By default, this is false.

Here is an example configuration:

{
    "capitalized-comments": [
        "error",
        "always",
        {
            "ignorePattern": "pragma|ignored",
            "ignoreInlineComments": true
        }
    ]
}

"always"

Using the "always" option means that this rule will report any comments which start with a lowercase letter. This is the default configuration for this rule.

Note that configuration comments and comments which start with URLs are never reported.

Examples of incorrect code for this rule:

/* eslint capitalized-comments: ["error", "always"] */

// lowercase comment

Examples of correct code for this rule:

/* eslint capitalized-comments: ["error", "always"] */

// Capitalized comment

// 1. Non-letter at beginning of comment

// 丈 Non-Latin character at beginning of comment

/* eslint semi:off */
/* eslint-env node */
/* eslint-disable */
/* eslint-enable */
/* istanbul ignore next */
/* jscs:enable */
/* jshint asi:true */
/* global foo */
/* globals foo */
/* exported myVar */
// eslint-disable-line
// eslint-disable-next-line
// https://github.com

"never"

Using the "never" option means that this rule will report any comments which start with an uppercase letter.

Examples of incorrect code with the "never" option:

/* eslint capitalized-comments: ["error", "never"] */

// Capitalized comment

Examples of correct code with the "never" option:

/* eslint capitalized-comments: ["error", "never"] */

// lowercase comment

// 1. Non-letter at beginning of comment

// 丈 Non-Latin character at beginning of comment

ignorePattern

The ignorePattern object takes a string value, which is used as a regular expression applied to the first word of a comment.

Examples of correct code with the "ignorePattern" option set to "pragma":

/* eslint capitalized-comments: ["error", "always", { "ignorePattern": "pragma" }] */

function foo() {
    /* pragma wrap(true) */
}

ignoreInlineComments

Setting the ignoreInlineComments option to true means that comments in the middle of code (with a token on the same line as the beginning of the comment, and another token on the same line as the end of the comment) will not be reported by this rule.

Examples of correct code with the "ignoreInlineComments" option set to true:

/* eslint capitalized-comments: ["error", "always", { "ignoreInlineComments": true }] */

function foo(/* ignored */ a) {
}

ignoreConsecutiveComments

If the ignoreConsecutiveComments option is set to true, then comments which otherwise violate the rule will not be reported as long as they immediately follow another comment. This can be applied more than once.

Examples of correct code with ignoreConsecutiveComments set to true:

/* eslint capitalize-comments: ["error", "always", { "ignoreConsecutiveComments": true }] */

// This comment is valid since it has the correct capitalization.
// this comment is ignored since it follows another comment,
// and this one as well because it follows yet another comment.

/* Here is a block comment which has the correct capitalization, */
/* but this one is ignored due to being consecutive; */
/*
 * in fact, even if any of these are multi-line, that is fine too.
 */

Examples of incorrect code with ignoreConsecutiveComments set to true:

/* eslint capitalize-comments: ["error", "always", { "ignoreConsecutiveComments": true }] */

// this comment is invalid, but only on this line.
// this comment does NOT get reported, since it is a consecutive comment.

Using Different Options for Line and Block Comments

If you wish to have a different configuration for line comments and block comments, you can do so by using two different object configurations (note that the capitalization option will be enforced consistently for line and block comments):

{
    "capitalized-comments": [
        "error",
        "always",
        {
            "line": {
                "ignorePattern": "pragma|ignored",
            },
            "block": {
                "ignoreInlineComments": true,
                "ignorePattern": "ignored"
            }
        }
    ]
}

Examples of incorrect code with different line and block comment configuration:

/* eslint capitalized-comments: ["error", "always", { "block": { "ignorePattern": "blockignore" } }] */

// capitalized line comment, this is incorrect, blockignore does not help here
/* lowercased block comment, this is incorrect too */

Examples of correct code with different line and block comment configuration:

/* eslint capitalized-comments: ["error", "always", { "block": { "ignorePattern": "blockignore" } }] */

// Uppercase line comment, this is correct
/* blockignore lowercase block comment, this is correct due to ignorePattern */

When Not To Use It

This rule can be disabled if you do not care about the grammatical style of comments in your codebase.

Compatibility

• JSCS: requireCapitalizedComments and disallowCapitalizedComments Source: http://eslint.org/docs/rules/

        // jogwheel does not support asynchronously running animations

Close

enforce or disallow capitalization of the first letter of a comment (capitalized-comments)

Comments are useful for leaving information for future developers. In order for that information to be useful and not distracting, it is sometimes desirable for comments to follow a particular style. One element of comment formatting styles is whether the first word of a comment should be capitalized or lowercase.

In general, no comment style is any more or less valid than any others, but many developers would agree that a consistent style can improve a project's maintainability.

Rule Details

This rule aims to enforce a consistent style of comments across your codebase, specifically by either requiring or disallowing a capitalized letter as the first word character in a comment. This rule will not issue warnings when non-cased letters are used.

By default, this rule will require a non-lowercase letter at the beginning of comments.

Examples of incorrect code for this rule:

/* eslint capitalized-comments: ["error"] */

// lowercase comment

Examples of correct code for this rule:

// Capitalized comment

// 1. Non-letter at beginning of comment

// 丈 Non-Latin character at beginning of comment

/* eslint semi:off */
/* eslint-env node */
/* eslint-disable */
/* eslint-enable */
/* istanbul ignore next */
/* jscs:enable */
/* jshint asi:true */
/* global foo */
/* globals foo */
/* exported myVar */
// eslint-disable-line
// eslint-disable-next-line
// https://github.com

Options

This rule has two options: a string value "always" or "never" which determines whether capitalization of the first word of a comment should be required or forbidden, and optionally an object containing more configuration parameters for the rule.

Here are the supported object options:

• ignorePattern: A string representing a regular expression pattern of words that should be ignored by this rule. If the first word of a comment matches the pattern, this rule will not report that comment.
  • Note that the following words are always ignored by this rule: ["jscs", "jshint", "eslint", "istanbul", "global", "globals", "exported"].
• ignoreInlineComments: If this is true, the rule will not report on comments in the middle of code. By default, this is false.
• ignoreConsecutiveComments: If this is true, the rule will not report on a comment which violates the rule, as long as the comment immediately follows another comment. By default, this is false.

Here is an example configuration:

{
    "capitalized-comments": [
        "error",
        "always",
        {
            "ignorePattern": "pragma|ignored",
            "ignoreInlineComments": true
        }
    ]
}

"always"

Using the "always" option means that this rule will report any comments which start with a lowercase letter. This is the default configuration for this rule.

Note that configuration comments and comments which start with URLs are never reported.

Examples of incorrect code for this rule:

/* eslint capitalized-comments: ["error", "always"] */

// lowercase comment

Examples of correct code for this rule:

/* eslint capitalized-comments: ["error", "always"] */

// Capitalized comment

// 1. Non-letter at beginning of comment

// 丈 Non-Latin character at beginning of comment

/* eslint semi:off */
/* eslint-env node */
/* eslint-disable */
/* eslint-enable */
/* istanbul ignore next */
/* jscs:enable */
/* jshint asi:true */
/* global foo */
/* globals foo */
/* exported myVar */
// eslint-disable-line
// eslint-disable-next-line
// https://github.com

"never"

Using the "never" option means that this rule will report any comments which start with an uppercase letter.

Examples of incorrect code with the "never" option:

/* eslint capitalized-comments: ["error", "never"] */

// Capitalized comment

Examples of correct code with the "never" option:

/* eslint capitalized-comments: ["error", "never"] */

// lowercase comment

// 1. Non-letter at beginning of comment

// 丈 Non-Latin character at beginning of comment

ignorePattern

The ignorePattern object takes a string value, which is used as a regular expression applied to the first word of a comment.

Examples of correct code with the "ignorePattern" option set to "pragma":

/* eslint capitalized-comments: ["error", "always", { "ignorePattern": "pragma" }] */

function foo() {
    /* pragma wrap(true) */
}

ignoreInlineComments

Setting the ignoreInlineComments option to true means that comments in the middle of code (with a token on the same line as the beginning of the comment, and another token on the same line as the end of the comment) will not be reported by this rule.

Examples of correct code with the "ignoreInlineComments" option set to true:

/* eslint capitalized-comments: ["error", "always", { "ignoreInlineComments": true }] */

function foo(/* ignored */ a) {
}

ignoreConsecutiveComments

If the ignoreConsecutiveComments option is set to true, then comments which otherwise violate the rule will not be reported as long as they immediately follow another comment. This can be applied more than once.

Examples of correct code with ignoreConsecutiveComments set to true:

/* eslint capitalize-comments: ["error", "always", { "ignoreConsecutiveComments": true }] */

// This comment is valid since it has the correct capitalization.
// this comment is ignored since it follows another comment,
// and this one as well because it follows yet another comment.

/* Here is a block comment which has the correct capitalization, */
/* but this one is ignored due to being consecutive; */
/*
 * in fact, even if any of these are multi-line, that is fine too.
 */

Examples of incorrect code with ignoreConsecutiveComments set to true:

/* eslint capitalize-comments: ["error", "always", { "ignoreConsecutiveComments": true }] */

// this comment is invalid, but only on this line.
// this comment does NOT get reported, since it is a consecutive comment.

Using Different Options for Line and Block Comments

If you wish to have a different configuration for line comments and block comments, you can do so by using two different object configurations (note that the capitalization option will be enforced consistently for line and block comments):

{
    "capitalized-comments": [
        "error",
        "always",
        {
            "line": {
                "ignorePattern": "pragma|ignored",
            },
            "block": {
                "ignoreInlineComments": true,
                "ignorePattern": "ignored"
            }
        }
    ]
}

Examples of incorrect code with different line and block comment configuration:

/* eslint capitalized-comments: ["error", "always", { "block": { "ignorePattern": "blockignore" } }] */

// capitalized line comment, this is incorrect, blockignore does not help here
/* lowercased block comment, this is incorrect too */

Examples of correct code with different line and block comment configuration:

/* eslint capitalized-comments: ["error", "always", { "block": { "ignorePattern": "blockignore" } }] */

// Uppercase line comment, this is correct
/* blockignore lowercase block comment, this is correct due to ignorePattern */

When Not To Use It

This rule can be disabled if you do not care about the grammatical style of comments in your codebase.

Compatibility

• JSCS: requireCapitalizedComments and disallowCapitalizedComments Source: http://eslint.org/docs/rules/

        elements.map(element => element.style[prefix('animationName', window, document)] = '');

Close

Disallow Assignment in return Statement (no-return-assign)

One of the interesting, and sometimes confusing, aspects of JavaScript is that assignment can happen at almost any point. Because of this, an errant equals sign can end up causing assignment when the true intent was to do a comparison. This is especially true when using a return statement. For example:

function doSomething() {
    return foo = bar + 2;
}

It is difficult to tell the intent of the return statement here. It's possible that the function is meant to return the result of bar + 2, but then why is it assigning to foo? It's also possible that the intent was to use a comparison operator such as == and that this code is an error.

Because of this ambiguity, it's considered a best practice to not use assignment in return statements.

Rule Details

This rule aims to eliminate assignments from return statements. As such, it will warn whenever an assignment is found as part of return.

Options

The rule takes one option, a string, which must contain one of the following values:

• except-parens (default): Disallow assignments unless they are enclosed in parentheses.
• always: Disallow all assignments.

except-parens

This is the default option. It disallows assignments unless they are enclosed in parentheses.

Examples of incorrect code for the default "except-parens" option:

/*eslint no-return-assign: "error"*/

function doSomething() {
    return foo = bar + 2;
}

function doSomething() {
    return foo += 2;
}

Examples of correct code for the default "except-parens" option:

/*eslint no-return-assign: "error"*/

function doSomething() {
    return foo == bar + 2;
}

function doSomething() {
    return foo === bar + 2;
}

function doSomething() {
    return (foo = bar + 2);
}

always

This option disallows all assignments in return statements. All assignments are treated as problems.

Examples of incorrect code for the "always" option:

/*eslint no-return-assign: ["error", "always"]*/

function doSomething() {
    return foo = bar + 2;
}

function doSomething() {
    return foo += 2;
}

function doSomething() {
    return (foo = bar + 2);
}

Examples of correct code for the "always" option:

/*eslint no-return-assign: ["error", "always"]*/

function doSomething() {
    return foo == bar + 2;
}

function doSomething() {
    return foo === bar + 2;
}

When Not To Use It

If you want to allow the use of assignment operators in a return statement, then you can safely disable this rule. Source: http://eslint.org/docs/rules/

        elements.map(element =>

Close

Disallow Assignment in return Statement (no-return-assign)

One of the interesting, and sometimes confusing, aspects of JavaScript is that assignment can happen at almost any point. Because of this, an errant equals sign can end up causing assignment when the true intent was to do a comparison. This is especially true when using a return statement. For example:

function doSomething() {
    return foo = bar + 2;
}

It is difficult to tell the intent of the return statement here. It's possible that the function is meant to return the result of bar + 2, but then why is it assigning to foo? It's also possible that the intent was to use a comparison operator such as == and that this code is an error.

Because of this ambiguity, it's considered a best practice to not use assignment in return statements.

Rule Details

This rule aims to eliminate assignments from return statements. As such, it will warn whenever an assignment is found as part of return.

Options

The rule takes one option, a string, which must contain one of the following values:

• except-parens (default): Disallow assignments unless they are enclosed in parentheses.
• always: Disallow all assignments.

except-parens

This is the default option. It disallows assignments unless they are enclosed in parentheses.

Examples of incorrect code for the default "except-parens" option:

/*eslint no-return-assign: "error"*/

function doSomething() {
    return foo = bar + 2;
}

function doSomething() {
    return foo += 2;
}

Examples of correct code for the default "except-parens" option:

/*eslint no-return-assign: "error"*/

function doSomething() {
    return foo == bar + 2;
}

function doSomething() {
    return foo === bar + 2;
}

function doSomething() {
    return (foo = bar + 2);
}

always

This option disallows all assignments in return statements. All assignments are treated as problems.

Examples of incorrect code for the "always" option:

/*eslint no-return-assign: ["error", "always"]*/

function doSomething() {
    return foo = bar + 2;
}

function doSomething() {
    return foo += 2;
}

function doSomething() {
    return (foo = bar + 2);
}

Examples of correct code for the "always" option:

/*eslint no-return-assign: ["error", "always"]*/

function doSomething() {
    return foo == bar + 2;
}

function doSomething() {
    return foo === bar + 2;
}

When Not To Use It

If you want to allow the use of assignment operators in a return statement, then you can safely disable this rule. Source: http://eslint.org/docs/rules/