no-irregular-whitespace

Disallow irregular whitespace

Invalid or irregular whitespace causes issues with ECMAScript 5 parsers and also makes code harder to debug in a similar nature to mixed tabs and spaces.

Various whitespace characters can be inputted by programmers by mistake for example from copying or keyboard shortcuts. Pressing Alt + Space on macOS adds in a non breaking space character for example.

A simple fix for this problem could be to rewrite the offending line from scratch. This might also be a problem introduced by the text editor: if rewriting the line does not fix it, try using a different editor.

Known issues these spaces cause:

• Zero Width Space
  • Is NOT considered a separator for tokens and is often parsed as an Unexpected token ILLEGAL
  • Is NOT shown in modern browsers making code repository software expected to resolve the visualization
• Line Separator
  • Is NOT a valid character within JSON which would cause parse errors

Rule Details

This rule is aimed at catching invalid whitespace that is not a normal tab and space. Some of these characters may cause issues in modern browsers and others will be a debugging issue to spot.

This rule disallows the following characters except where the options allow:

\u000B - Line Tabulation (\v) - <VT>
\u000C - Form Feed (\f) - <FF>
\u00A0 - No-Break Space - <NBSP>
\u0085 - Next Line
\u1680 - Ogham Space Mark
\u180E - Mongolian Vowel Separator - <MVS>
\ufeff - Zero Width No-Break Space - <BOM>
\u2000 - En Quad
\u2001 - Em Quad
\u2002 - En Space - <ENSP>
\u2003 - Em Space - <EMSP>
\u2004 - Three-Per-Em
\u2005 - Four-Per-Em
\u2006 - Six-Per-Em
\u2007 - Figure Space
\u2008 - Punctuation Space - <PUNCSP>
\u2009 - Thin Space
\u200A - Hair Space
\u200B - Zero Width Space - <ZWSP>
\u2028 - Line Separator
\u2029 - Paragraph Separator
\u202F - Narrow No-Break Space
\u205f - Medium Mathematical Space
\u3000 - Ideographic Space

Options

This rule has an object option for exceptions:

• "skipStrings": true (default) allows any whitespace characters in string literals
• "skipComments": true allows any whitespace characters in comments
• "skipRegExps": true allows any whitespace characters in regular expression literals
• "skipTemplates": true allows any whitespace characters in template literals

skipStrings

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

/*eslint no-irregular-whitespace: "error"*/

function thing() /*<NBSP>*/{
    return 'test';
}

function thing( /*<NBSP>*/){
    return 'test';
}

function thing /*<NBSP>*/(){
    return 'test';
}

function thing᠎/*<MVS>*/(){
    return 'test';
}

function thing() {
    return 'test'; /*<ENSP>*/
}

function thing() {
    return 'test'; /*<NBSP>*/
}

function thing() {
    // Description <NBSP>: some descriptive text
}

/*
Description <NBSP>: some descriptive text
*/

function thing() {
    return / <NBSP>regexp/;
}

/*eslint-env es6*/
function thing() {
    return `template <NBSP>string`;
}

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

/*eslint no-irregular-whitespace: "error"*/

function thing() {
    return ' <NBSP>thing';
}

function thing() {
    return '​<ZWSP>thing';
}

function thing() {
    return 'th <NBSP>ing';
}

skipComments

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

/*eslint no-irregular-whitespace: ["error", { "skipComments": true }]*/

function thing() {
    // Description <NBSP>: some descriptive text
}

/*
Description <NBSP>: some descriptive text
*/

skipRegExps

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

/*eslint no-irregular-whitespace: ["error", { "skipRegExps": true }]*/

function thing() {
    return / <NBSP>regexp/;
}

skipTemplates

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

/*eslint no-irregular-whitespace: ["error", { "skipTemplates": true }]*/
/*eslint-env es6*/

function thing() {
    return `template <NBSP>string`;
}

When Not To Use It

If you decide that you wish to use whitespace other than tabs and spaces outside of strings in your application.

Version

This rule was introduced in ESLint v0.9.0.

Further Reading

Resources

• Rule source
• Tests source