eslint/docs/rules/semi-spacing.md

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