eslint/docs/src/rules/no-irregular-whitespace.md

   1 ---
   2 title: no-irregular-whitespace
   3 layout: doc
   4 rule_type: problem
   5 further_reading:
   6 - https://es5.github.io/#x7.2
   7 - https://web.archive.org/web/20200414142829/http://timelessrepo.com/json-isnt-a-javascript-subset
   8 ---
   9
  10
  11
  12 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.
  13
  14 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.
  15
  16 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.
  17
  18 Known issues these spaces cause:
  19
  20 * Zero Width Space
  21     * Is NOT considered a separator for tokens and is often parsed as an `Unexpected token ILLEGAL`
  22     * Is NOT shown in modern browsers making code repository software expected to resolve the visualization
  23 * Line Separator
  24     * Is NOT a valid character within JSON which would cause parse errors
  25
  26 ## Rule Details
  27
  28 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.
  29
  30 This rule disallows the following characters except where the options allow:
  31
  32 ```text
  33 \u000B - Line Tabulation (\v) - <VT>
  34 \u000C - Form Feed (\f) - <FF>
  35 \u00A0 - No-Break Space - <NBSP>
  36 \u0085 - Next Line
  37 \u1680 - Ogham Space Mark
  38 \u180E - Mongolian Vowel Separator - <MVS>
  39 \ufeff - Zero Width No-Break Space - <BOM>
  40 \u2000 - En Quad
  41 \u2001 - Em Quad
  42 \u2002 - En Space - <ENSP>
  43 \u2003 - Em Space - <EMSP>
  44 \u2004 - Three-Per-Em
  45 \u2005 - Four-Per-Em
  46 \u2006 - Six-Per-Em
  47 \u2007 - Figure Space
  48 \u2008 - Punctuation Space - <PUNCSP>
  49 \u2009 - Thin Space
  50 \u200A - Hair Space
  51 \u200B - Zero Width Space - <ZWSP>
  52 \u2028 - Line Separator
  53 \u2029 - Paragraph Separator
  54 \u202F - Narrow No-Break Space
  55 \u205f - Medium Mathematical Space
  56 \u3000 - Ideographic Space
  57 ```
  58
  59 ## Options
  60
  61 This rule has an object option for exceptions:
  62
  63 * `"skipStrings": true` (default) allows any whitespace characters in string literals
  64 * `"skipComments": true` allows any whitespace characters in comments
  65 * `"skipRegExps": true` allows any whitespace characters in regular expression literals
  66 * `"skipTemplates": true` allows any whitespace characters in template literals
  67
  68 ### skipStrings
  69
  70 Examples of **incorrect** code for this rule with the default `{ "skipStrings": true }` option:
  71
  72 ::: incorrect
  73
  74 ```js
  75 /*eslint no-irregular-whitespace: "error"*/
  76
  77 function thing() /*<NBSP>*/{
  78     return 'test';
  79 }
  80
  81 function thing( /*<NBSP>*/){
  82     return 'test';
  83 }
  84
  85 function thing /*<NBSP>*/(){
  86     return 'test';
  87 }
  88
  89 function thing᠎/*<MVS>*/(){
  90     return 'test';
  91 }
  92
  93 function thing() {
  94     return 'test'; /*<ENSP>*/
  95 }
  96
  97 function thing() {
  98     return 'test'; /*<NBSP>*/
  99 }
 100
 101 function thing() {
 102     // Description <NBSP>: some descriptive text
 103 }
 104
 105 /*
 106 Description <NBSP>: some descriptive text
 107 */
 108
 109 function thing() {
 110     return / <NBSP>regexp/;
 111 }
 112
 113 /*eslint-env es6*/
 114 function thing() {
 115     return `template <NBSP>string`;
 116 }
 117 ```
 118
 119 :::
 120
 121 Examples of **correct** code for this rule with the default `{ "skipStrings": true }` option:
 122
 123 ::: correct
 124
 125 ```js
 126 /*eslint no-irregular-whitespace: "error"*/
 127
 128 function thing() {
 129     return ' <NBSP>thing';
 130 }
 131
 132 function thing() {
 133     return '<ZWSP>thing';
 134 }
 135
 136 function thing() {
 137     return 'th <NBSP>ing';
 138 }
 139 ```
 140
 141 :::
 142
 143 ### skipComments
 144
 145 Examples of additional **correct** code for this rule with the `{ "skipComments": true }` option:
 146
 147 ::: correct
 148
 149 ```js
 150 /*eslint no-irregular-whitespace: ["error", { "skipComments": true }]*/
 151
 152 function thing() {
 153     // Description <NBSP>: some descriptive text
 154 }
 155
 156 /*
 157 Description <NBSP>: some descriptive text
 158 */
 159 ```
 160
 161 :::
 162
 163 ### skipRegExps
 164
 165 Examples of additional **correct** code for this rule with the `{ "skipRegExps": true }` option:
 166
 167 ::: correct
 168
 169 ```js
 170 /*eslint no-irregular-whitespace: ["error", { "skipRegExps": true }]*/
 171
 172 function thing() {
 173     return / <NBSP>regexp/;
 174 }
 175 ```
 176
 177 :::
 178
 179 ### skipTemplates
 180
 181 Examples of additional **correct** code for this rule with the `{ "skipTemplates": true }` option:
 182
 183 ::: correct
 184
 185 ```js
 186 /*eslint no-irregular-whitespace: ["error", { "skipTemplates": true }]*/
 187 /*eslint-env es6*/
 188
 189 function thing() {
 190     return `template <NBSP>string`;
 191 }
 192 ```
 193
 194 :::
 195
 196 ## When Not To Use It
 197
 198 If you decide that you wish to use whitespace other than tabs and spaces outside of strings in your application.