eslint/docs/src/rules/no-arrow-condition.md

   1 ---
   2 title: no-arrow-condition
   3 layout: doc
   4
   5 related_rules:
   6 - arrow-parens
   7 - no-confusing-arrow
   8 - no-constant-condition
   9 ---
  10
  11 Disallows arrow functions where test conditions are expected.
  12
  13 (removed) This rule was **removed** in ESLint v2.0 and **replaced** by a combination of the [no-confusing-arrow](no-confusing-arrow) and [no-constant-condition](no-constant-condition) rules.
  14
  15 Arrow functions (`=>`) are similar in syntax to some comparison operators (`>`, `<`, `<=`, and `>=`). This rule warns against using the arrow function syntax in places where a condition is expected. Even if the arguments of the arrow function are wrapped with parens, this rule still warns about it.
  16
  17 Here's an example where the usage of `=>` is most likely a typo:
  18
  19 ```js
  20 // This is probably a typo
  21 if (a => 1) {}
  22 // And should instead be
  23 if (a >= 1) {}
  24 ```
  25
  26 There are also cases where the usage of `=>` can be ambiguous and should be rewritten to more clearly show the author's intent:
  27
  28 ```js
  29 // The intent is not clear
  30 var x = a => 1 ? 2 : 3
  31 // Did the author mean this
  32 var x = function (a) { return a >= 1 ? 2 : 3 }
  33 // Or this
  34 var x = a <= 1 ? 2 : 3
  35 ```
  36
  37 ## Rule Details
  38
  39 Examples of **incorrect** code for this rule:
  40
  41 :::incorrect
  42
  43 ```js
  44 /*eslint no-arrow-condition: "error"*/
  45 /*eslint-env es6*/
  46
  47 if (a => 1) {}
  48 while (a => 1) {}
  49 for (var a = 1; a => 10; a++) {}
  50 a => 1 ? 2 : 3
  51 (a => 1) ? 2 : 3
  52 var x = a => 1 ? 2 : 3
  53 var x = (a) => 1 ? 2 : 3
  54 ```
  55
  56 :::