eslint/docs/rules/no-confusing-arrow.md

   1 # Disallow arrow functions where they could be confused with comparisons (no-confusing-arrow)
   2
   3 Arrow functions (`=>`) are similar in syntax to some comparison operators (`>`, `<`, `<=`, and `>=`). This rule warns against using the arrow function syntax in places where it could be confused with a comparison operator.
   4
   5 Here's an example where the usage of `=>` could be confusing:
   6
   7 ```js
   8 // The intent is not clear
   9 var x = a => 1 ? 2 : 3;
  10 // Did the author mean this
  11 var x = function (a) { return 1 ? 2 : 3 };
  12 // Or this
  13 var x = a <= 1 ? 2 : 3;
  14 ```
  15
  16 ## Rule Details
  17
  18 Examples of **incorrect** code for this rule:
  19
  20 ```js
  21 /*eslint no-confusing-arrow: "error"*/
  22 /*eslint-env es6*/
  23
  24 var x = a => 1 ? 2 : 3;
  25 var x = (a) => 1 ? 2 : 3;
  26 ```
  27
  28 Examples of **correct** code for this rule:
  29
  30 ```js
  31 /*eslint no-confusing-arrow: "error"*/
  32 /*eslint-env es6*/
  33
  34 var x = a => (1 ? 2 : 3);
  35 var x = (a) => (1 ? 2 : 3);
  36 var x = a => { return 1 ? 2 : 3; };
  37 var x = (a) => { return 1 ? 2 : 3; };
  38 ```
  39
  40 ## Options
  41
  42 This rule accepts a single options argument with the following defaults:
  43
  44 ```json
  45 {
  46     "rules": {
  47         "no-confusing-arrow": ["error", {"allowParens": true}]
  48     }
  49 }
  50 ```
  51
  52 `allowParens` is a boolean setting that can be `true`(default) or `false`:
  53
  54 1. `true` relaxes the rule and accepts parenthesis as a valid "confusion-preventing" syntax.
  55 2. `false` warns even if the expression is wrapped in parenthesis
  56
  57 Examples of **incorrect** code for this rule with the `{"allowParens": false}` option:
  58
  59 ```js
  60 /*eslint no-confusing-arrow: ["error", {"allowParens": false}]*/
  61 /*eslint-env es6*/
  62 var x = a => (1 ? 2 : 3);
  63 var x = (a) => (1 ? 2 : 3);
  64 ```
  65
  66 ## Related Rules
  67
  68 * [no-constant-condition](no-constant-condition.md)
  69 * [arrow-parens](arrow-parens.md)