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require empty lines around comments (lines-around-comment)

Many style guides require empty lines before or after comments. The primary goal of these rules is to make the comments easier to read and improve readability of the code.

Rule Details

This rule requires empty lines before and/or after comments. It can be enabled separately for both block (/*) and line (//) comments. This rule does not apply to comments that appear on the same line as code and does not require empty lines at the beginning or end of a file.

Options

This rule has an object option:

  • "beforeBlockComment": true (default) requires an empty line before block comments
  • "afterBlockComment": true requires an empty line after block comments
  • "beforeLineComment": true requires an empty line before line comments
  • "afterLineComment": true requires an empty line after line comments
  • "allowBlockStart": true allows comments to appear at the start of block statements
  • "allowBlockEnd": true allows comments to appear at the end of block statements
  • "allowObjectStart": true allows comments to appear at the start of object literals
  • "allowObjectEnd": true allows comments to appear at the end of object literals
  • "allowArrayStart": true allows comments to appear at the start of array literals
  • "allowArrayEnd": true allows comments to appear at the end of array literals
  • "allowClassStart": true allows comments to appear at the start of classes
  • "allowClassEnd": true allows comments to appear at the end of classes
  • "applyDefaultIgnorePatterns" enables or disables the default comment patterns to be ignored by the rule
  • "ignorePattern" custom patterns to be ignored by the rule

beforeBlockComment

Examples of incorrect code for this rule with the default { "beforeBlockComment": true } option:

/*eslint lines-around-comment: ["error", { "beforeBlockComment": true }]*/

var night = "long";
/* what a great and wonderful day */
var day = "great"

Examples of correct code for this rule with the default { "beforeBlockComment": true } option:

/*eslint lines-around-comment: ["error", { "beforeBlockComment": true }]*/

var night = "long";

/* what a great and wonderful day */
var day = "great"

afterBlockComment

Examples of incorrect code for this rule with the { "afterBlockComment": true } option:

/*eslint lines-around-comment: ["error", { "afterBlockComment": true }]*/

var night = "long";

/* what a great and wonderful day */
var day = "great"

Examples of correct code for this rule with the { "afterBlockComment": true } option:

/*eslint lines-around-comment: ["error", { "afterBlockComment": true }]*/

var night = "long";

/* what a great and wonderful day */

var day = "great"

beforeLineComment

Examples of incorrect code for this rule with the { "beforeLineComment": true } option:

/*eslint lines-around-comment: ["error", { "beforeLineComment": true }]*/

var night = "long";
// what a great and wonderful day
var day = "great"

Examples of correct code for this rule with the { "beforeLineComment": true } option:

/*eslint lines-around-comment: ["error", { "beforeLineComment": true }]*/

var night = "long";

// what a great and wonderful day
var day = "great"

afterLineComment

Examples of incorrect code for this rule with the { "afterLineComment": true } option:

/*eslint lines-around-comment: ["error", { "afterLineComment": true }]*/

var night = "long";
// what a great and wonderful day
var day = "great"

Examples of correct code for this rule with the { "afterLineComment": true } option:

/*eslint lines-around-comment: ["error", { "afterLineComment": true }]*/

var night = "long";
// what a great and wonderful day

var day = "great"

allowBlockStart

Examples of correct code for this rule with the { "beforeLineComment": true, "allowBlockStart": true } options:

/*eslint lines-around-comment: ["error", { "beforeLineComment": true, "allowBlockStart": true }]*/

function foo(){
    // what a great and wonderful day
    var day = "great"
    return day;
}

Examples of correct code for this rule with the { "beforeBlockComment": true, "allowBlockStart": true } options:

/*eslint lines-around-comment: ["error", { "beforeBlockComment": true, "allowBlockStart": true }]*/

function foo(){
    /* what a great and wonderful day */
    var day = "great"
    return day;
}

allowBlockEnd

Examples of correct code for this rule with the { "afterLineComment": true, "allowBlockEnd": true } option:

/*eslint lines-around-comment: ["error", { "afterLineComment": true, "allowBlockEnd": true }]*/

function foo(){
    var day = "great"
    return day;
    // what a great and wonderful day
}

Examples of correct code for this rule with the { "afterBlockComment": true, "allowBlockEnd": true } option:

/*eslint lines-around-comment: ["error", { "afterBlockComment": true, "allowBlockEnd": true }]*/

function foo(){
    var day = "great"
    return day;

    /* what a great and wonderful day */
}

allowClassStart

Examples of incorrect code for this rule with the { "beforeLineComment": true, "allowClassStart": false } option:

/*eslint lines-around-comment: ["error", { "beforeLineComment": true, "allowClassStart": false }]*/

class foo {
    // what a great and wonderful day
    day() {}
};

Examples of correct code for this rule with the { "beforeLineComment": true, "allowClassStart": false } option:

/*eslint lines-around-comment: ["error", { "beforeLineComment": true, "allowClassStart": false }]*/

class foo {

    // what a great and wonderful day
    day() {}
};

Examples of correct code for this rule with the { "beforeLineComment": true, "allowClassStart": true } option:

/*eslint lines-around-comment: ["error", { "beforeLineComment": true, "allowClassStart": true }]*/

class foo {
    // what a great and wonderful day
    day() {}
};

Examples of incorrect code for this rule with the { "beforeBlockComment": true, "allowClassStart": false } option:

/*eslint lines-around-comment: ["error", { "beforeBlockComment": true, "allowClassStart": false }]*/

class foo {
    /* what a great and wonderful day */
    day() {}
};

Examples of correct code for this rule with the { "beforeBlockComment": true, "allowClassStart": false } option:

/*eslint lines-around-comment: ["error", { "beforeBlockComment": true, "allowClassStart": false }]*/

class foo {

    /* what a great and wonderful day */
    day() {}
};

Examples of correct code for this rule with the { "beforeBlockComment": true, "allowClassStart": true } option:

/*eslint lines-around-comment: ["error", { "beforeBlockComment": true, "allowClassStart": true }]*/

class foo {
    /* what a great and wonderful day */
    day() {}
};

allowClassEnd

Examples of correct code for this rule with the { "afterLineComment": true, "allowClassEnd": true } option:

/*eslint lines-around-comment: ["error", { "afterLineComment": true, "allowClassEnd": true }]*/

class foo {
    day() {}
    // what a great and wonderful day
};

Examples of correct code for this rule with the { "afterBlockComment": true, "allowClassEnd": true } option:

/*eslint lines-around-comment: ["error", { "afterBlockComment": true, "allowClassEnd": true }]*/

class foo {
    day() {}

    /* what a great and wonderful day */
};

allowObjectStart

Examples of correct code for this rule with the { "beforeLineComment": true, "allowObjectStart": true } option:

/*eslint lines-around-comment: ["error", { "beforeLineComment": true, "allowObjectStart": true }]*/

var foo = {
    // what a great and wonderful day
    day: "great"
};

const {
    // what a great and wonderful day
    foo: someDay
} = {foo: "great"};

const {
    // what a great and wonderful day
    day
} = {day: "great"};

Examples of correct code for this rule with the { "beforeBlockComment": true, "allowObjectStart": true } option:

/*eslint lines-around-comment: ["error", { "beforeBlockComment": true, "allowObjectStart": true }]*/

var foo = {
    /* what a great and wonderful day */
    day: "great"
};

const {
    /* what a great and wonderful day */
    foo: someDay
} = {foo: "great"};

const {
    /* what a great and wonderful day */
    day
} = {day: "great"};

allowObjectEnd

Examples of correct code for this rule with the { "afterLineComment": true, "allowObjectEnd": true } option:

/*eslint lines-around-comment: ["error", { "afterLineComment": true, "allowObjectEnd": true }]*/

var foo = {
    day: "great"
    // what a great and wonderful day
};

const {
    foo: someDay
    // what a great and wonderful day
} = {foo: "great"};

const {
    day
    // what a great and wonderful day
} = {day: "great"};

Examples of correct code for this rule with the { "afterBlockComment": true, "allowObjectEnd": true } option:

/*eslint lines-around-comment: ["error", { "afterBlockComment": true, "allowObjectEnd": true }]*/

var foo = {
    day: "great"

    /* what a great and wonderful day */
};

const {
    foo: someDay

    /* what a great and wonderful day */
} = {foo: "great"};

const {
    day

    /* what a great and wonderful day */
} = {day: "great"};

allowArrayStart

Examples of correct code for this rule with the { "beforeLineComment": true, "allowArrayStart": true } option:

/*eslint lines-around-comment: ["error", { "beforeLineComment": true, "allowArrayStart": true }]*/

var day = [
    // what a great and wonderful day
    "great",
    "wonderful"
];

const [
    // what a great and wonderful day
    someDay
] = ["great", "not great"];

Examples of correct code for this rule with the { "beforeBlockComment": true, "allowArrayStart": true } option:

/*eslint lines-around-comment: ["error", { "beforeBlockComment": true, "allowArrayStart": true }]*/

var day = [
    /* what a great and wonderful day */
    "great",
    "wonderful"
];

const [
    /* what a great and wonderful day */
    someDay
] = ["great", "not great"];

allowArrayEnd

Examples of correct code for this rule with the { "afterLineComment": true, "allowArrayEnd": true } option:

/*eslint lines-around-comment: ["error", { "afterLineComment": true, "allowArrayEnd": true }]*/

var day = [
    "great",
    "wonderful"
    // what a great and wonderful day
];

const [
    someDay
    // what a great and wonderful day
] = ["great", "not great"];

Examples of correct code for this rule with the { "afterBlockComment": true, "allowArrayEnd": true } option:

/*eslint lines-around-comment: ["error", { "afterBlockComment": true, "allowArrayEnd": true }]*/

var day = [
    "great",
    "wonderful"

    /* what a great and wonderful day */
];

const [
    someDay

    /* what a great and wonderful day */
] = ["great", "not great"];

ignorePattern

By default this rule ignores comments starting with the following words: eslint, jshint, jslint, istanbul, global, exported, jscs. An alternative regular expression can be provided.

Examples of correct code for the ignorePattern option:

/*eslint lines-around-comment: ["error"]*/

foo();
/* eslint mentioned in this comment */,
bar();


/*eslint lines-around-comment: ["error", { "ignorePattern": "pragma" }] */

foo();
/* a valid comment using pragma in it */

Examples of incorrect code for the ignorePattern option:

/*eslint lines-around-comment: ["error", { "ignorePattern": "pragma" }] */

1 + 1;
/* something else */

applyDefaultIgnorePatterns

Default ignore patterns are applied even when ignorePattern is provided. If you want to omit default patterns, set this option to false.

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

/*eslint lines-around-comment: ["error", { "ignorePattern": "pragma", applyDefaultIgnorePatterns: false }] */

foo();
/* a valid comment using pragma in it */

Examples of incorrect code for the { "applyDefaultIgnorePatterns": false } option:

/*eslint lines-around-comment: ["error", { "applyDefaultIgnorePatterns": false }] */

foo();
/* eslint mentioned in comment */

When Not To Use It

Many people enjoy a terser code style and don't mind comments bumping up against code. If you fall into that category this rule is not for you.

Related Rules

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