eslint/docs/src/rules/semi-spacing.md

   1 ---
   2 title: semi-spacing
   3 layout: doc
   4 rule_type: layout
   5 related_rules:
   6 - semi
   7 - no-extra-semi
   8 - comma-spacing
   9 - block-spacing
  10 - space-in-parens
  11 ---
  12
  13
  14
  15 JavaScript allows you to place unnecessary spaces before or after a semicolon.
  16
  17 Disallowing or enforcing space around a semicolon can improve the readability of your program.
  18
  19 ```js
  20 var a = "b" ;
  21
  22 var c = "d";var e = "f";
  23 ```
  24
  25 ## Rule Details
  26
  27 This rule aims to enforce spacing around a semicolon. This rule prevents the use of spaces before a semicolon in expressions.
  28
  29 This rule doesn't check spacing in the following cases:
  30
  31 * The spacing after the semicolon if it is the first token in the line.
  32
  33 * The spacing before the semicolon if it is after an opening parenthesis (`(` or `{`), or the spacing after the semicolon if it is before a closing parenthesis (`)` or `}`). That spacing is checked by `space-in-parens` or `block-spacing`.
  34
  35 * The spacing around the semicolon in a for loop with an empty condition (`for(;;)`).
  36
  37 ## Options
  38
  39 The rule takes one option, an object, which has two keys `before` and `after` having boolean values `true` or `false`.
  40 If `before` is `true`, space is enforced before semicolons and if it's `false`, space is disallowed before semicolons.
  41 If `after` is `true`, space is enforced after semicolons and if it's `false`, space is disallowed after semicolons.
  42 The `after` option will be only applied if a semicolon is not at the end of line.
  43
  44 The default is `{"before": false, "after": true}`.
  45
  46 ```json
  47     "semi-spacing": ["error", {"before": false, "after": true}]
  48 ```
  49
  50 ### `{"before": false, "after": true}`
  51
  52 This is the default option. It enforces spacing after semicolons and disallows spacing before semicolons.
  53
  54 Examples of **incorrect** code for this rule:
  55
  56 ::: incorrect
  57
  58 ```js
  59 /*eslint semi-spacing: "error"*/
  60
  61 var foo ;
  62 var foo;var bar;
  63 throw new Error("error") ;
  64 while (a) { break ; }
  65 for (i = 0 ; i < 10 ; i++) {}
  66 for (i = 0;i < 10;i++) {}
  67 ```
  68
  69 :::
  70
  71 Examples of **correct** code for this rule:
  72
  73 ::: correct
  74
  75 ```js
  76 /*eslint semi-spacing: "error"*/
  77
  78 var foo;
  79 var foo; var bar;
  80 throw new Error("error");
  81 while (a) { break; }
  82 for (i = 0; i < 10; i++) {}
  83 for (;;) {}
  84 if (true) {;}
  85 ;foo();
  86 ```
  87
  88 :::
  89
  90 ### `{"before": true, "after": false}`
  91
  92 This option enforces spacing before semicolons and disallows spacing after semicolons.
  93
  94 Examples of **incorrect** code for this rule with the `{"before": true, "after": false}` option:
  95
  96 ::: incorrect
  97
  98 ```js
  99 /*eslint semi-spacing: ["error", { "before": true, "after": false }]*/
 100
 101 var foo;
 102 var foo ; var bar;
 103 throw new Error("error");
 104 while (a) { break; }
 105 for (i = 0;i < 10;i++) {}
 106 for (i = 0; i < 10; i++) {}
 107 ```
 108
 109 :::
 110
 111 Examples of **correct** code for this rule with the `{"before": true, "after": false}` option:
 112
 113 ::: correct
 114
 115 ```js
 116 /*eslint semi-spacing: ["error", { "before": true, "after": false }]*/
 117
 118 var foo ;
 119 var foo ;var bar ;
 120 throw new Error("error") ;
 121 while (a) {break ;}
 122 for (i = 0 ;i < 10 ;i++) {}
 123 ```
 124
 125 :::
 126
 127 ## When Not To Use It
 128
 129 You can turn this rule off if you are not concerned with the consistency of spacing before or after semicolons.