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Requires or disallows a whitespace (space or tab) beginning a comment (spaced-comment)

The --fix option on the command line can automatically fix some of the problems reported by this rule.

Some style guides require or disallow a whitespace immediately after the initial // or /* of a comment. Whitespace after the // or /* makes it easier to read text in comments. On the other hand, commenting out code is easier without having to put a whitespace right after the // or /*.

Rule Details

This rule will enforce consistency of spacing after the start of a comment // or /*. It also provides several exceptions for various documentation styles.

Options

The rule takes two options.

  • The first is a string which be either "always" or "never". The default is "always".

    • If "always" then the // or /* must be followed by at least one whitespace.

    • If "never" then there should be no whitespace following.

  • This rule can also take a 2nd option, an object with any of the following keys: "exceptions" and "markers".

    • The "exceptions" value is an array of string patterns which are considered exceptions to the rule. The rule will not warn when the pattern starts from the beginning of the comment and repeats until the end of the line or */ if the comment is a single line comment. Please note that exceptions are ignored if the first argument is "never".
    "spaced-comment": ["error", "always", { "exceptions": ["-", "+"] }]
    • The "markers" value is an array of string patterns which are considered markers for docblock-style comments, such as an additional /, used to denote documentation read by doxygen, vsdoc, etc. which must have additional characters. The "markers" array will apply regardless of the value of the first argument, e.g. "always" or "never".
    "spaced-comment": ["error", "always", { "markers": ["/"] }]

The difference between a marker and an exception is that a marker only appears at the beginning of the comment whereas exceptions can occur anywhere in the comment string.

You can also define separate exceptions and markers for block and line comments. The "block" object can have an additional key "balanced", a boolean that specifies if inline block comments should have balanced spacing. The default value is false.

  • If "balanced": true and "always" then the /* must be followed by at least one whitespace, and the */ must be preceded by at least one whitespace.

  • If "balanced": true and "never" then there should be no whitespace following /* or preceding */.

  • If "balanced": false then balanced whitespace is not enforced.

"spaced-comment": ["error", "always", {
    "line": {
        "markers": ["/"],
        "exceptions": ["-", "+"]
    },
    "block": {
        "markers": ["!"],
        "exceptions": ["*"],
        "balanced": true
    }
}]

always

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

/*eslint spaced-comment: ["error", "always"]*/

//This is a comment with no whitespace at the beginning

/*This is a comment with no whitespace at the beginning */
/* eslint spaced-comment: ["error", "always", { "block": { "balanced": true } }] */
/* This is a comment with whitespace at the beginning but not the end*/

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

/* eslint spaced-comment: ["error", "always"] */

// This is a comment with a whitespace at the beginning

/* This is a comment with a whitespace at the beginning */

/*
 * This is a comment with a whitespace at the beginning
 */

/*
This comment has a newline
*/
/* eslint spaced-comment: ["error", "always"] */

/**
* I am jsdoc
*/

never

Examples of incorrect code for this rule with the "never" option:

/*eslint spaced-comment: ["error", "never"]*/

// This is a comment with a whitespace at the beginning

/* This is a comment with a whitespace at the beginning */

/* \nThis is a comment with a whitespace at the beginning */
/*eslint spaced-comment: ["error", "never", { "block": { "balanced": true } }]*/
/*This is a comment with whitespace at the end */

Examples of correct code for this rule with the "never" option:

/*eslint spaced-comment: ["error", "never"]*/

/*This is a comment with no whitespace at the beginning */
/*eslint spaced-comment: ["error", "never"]*/

/**
* I am jsdoc
*/

exceptions

Examples of incorrect code for this rule with the "always" option combined with "exceptions":

/* eslint spaced-comment: ["error", "always", { "block": { "exceptions": ["-"] } }] */

//--------------
// Comment block
//--------------
/* eslint spaced-comment: ["error", "always", { "exceptions": ["-", "+"] }] */

//------++++++++
// Comment block
//------++++++++
/* eslint spaced-comment: ["error", "always", { "exceptions": ["-", "+"] }] */

/*------++++++++*/
/* Comment block */
/*------++++++++*/
/* eslint spaced-comment: ["error", "always", { "line": { "exceptions": ["-+"] } }] */

/*-+-+-+-+-+-+-+*/
// Comment block
/*-+-+-+-+-+-+-+*/
/* eslint spaced-comment: ["error", "always", { "block": { "exceptions": ["*"] } }] */

/******** COMMENT *******/

Examples of correct code for this rule with the "always" option combined with "exceptions":

/* eslint spaced-comment: ["error", "always", { "exceptions": ["-"] }] */

//--------------
// Comment block
//--------------
/* eslint spaced-comment: ["error", "always", { "line": { "exceptions": ["-"] } }] */

//--------------
// Comment block
//--------------
/* eslint spaced-comment: ["error", "always", { "exceptions": ["*"] }] */

/****************
 * Comment block
 ****************/
/* eslint spaced-comment: ["error", "always", { "exceptions": ["-+"] }] */

//-+-+-+-+-+-+-+
// Comment block
//-+-+-+-+-+-+-+

/*-+-+-+-+-+-+-+*/
// Comment block
/*-+-+-+-+-+-+-+*/
/* eslint spaced-comment: ["error", "always", { "block": { "exceptions": ["-+"] } }] */

/*-+-+-+-+-+-+-+*/
// Comment block
/*-+-+-+-+-+-+-+*/
/* eslint spaced-comment: ["error", "always", { "block": { "exceptions": ["*"] } }] */

/***************/

/********
COMMENT
*******/

markers

Examples of incorrect code for this rule with the "always" option combined with "markers":

/* eslint spaced-comment: ["error", "always", { "markers": ["/"] }] */

///This is a comment with a marker but without whitespace
/*eslint spaced-comment: ["error", "always", { "block": { "markers": ["!"], "balanced": true } }]*/
/*! This is a comment with a marker but without whitespace at the end*/
/*eslint spaced-comment: ["error", "never", { "block": { "markers": ["!"], "balanced": true } }]*/
/*!This is a comment with a marker but with whitespace at the end */

Examples of correct code for this rule with the "always" option combined with "markers":

/* eslint spaced-comment: ["error", "always", { "markers": ["/"] }] */

/// This is a comment with a marker
/*eslint spaced-comment: ["error", "never", { "markers": ["!<"] }]*/

//!<This is a line comment with a marker

/*!<this is a block comment with a marker
subsequent lines are ignored
*/
/* eslint spaced-comment: ["error", "always", { "markers": ["global"] }] */

/*global ABC*/

Version

This rule was introduced in ESLint 0.23.0.

Resources

© JS Foundation and other contributors
Licensed under the MIT License.
https://eslint.org/docs/rules/spaced-comment