eslint/docs/rules/complexity.md

   1 # Limit Cyclomatic Complexity (complexity)
   2
   3 Cyclomatic complexity measures the number of linearly independent paths through a program's source code. This rule allows setting a cyclomatic complexity threshold.
   4
   5 ```js
   6 function a(x) {
   7     if (true) {
   8         return x; // 1st path
   9     } else if (false) {
  10         return x+1; // 2nd path
  11     } else {
  12         return 4; // 3rd path
  13     }
  14 }
  15 ```
  16
  17 ## Rule Details
  18
  19 This rule is aimed at reducing code complexity by capping the amount of cyclomatic complexity allowed in a program. As such, it will warn when the cyclomatic complexity crosses the configured threshold (default is `20`).
  20
  21 Examples of **incorrect** code for a maximum of 2:
  22
  23 ```js
  24 /*eslint complexity: ["error", 2]*/
  25
  26 function a(x) {
  27     if (true) {
  28         return x;
  29     } else if (false) {
  30         return x+1;
  31     } else {
  32         return 4; // 3rd path
  33     }
  34 }
  35 ```
  36
  37 Examples of **correct** code for a maximum of 2:
  38
  39 ```js
  40 /*eslint complexity: ["error", 2]*/
  41
  42 function a(x) {
  43     if (true) {
  44         return x;
  45     } else {
  46         return 4;
  47     }
  48 }
  49 ```
  50
  51 ## Options
  52
  53 Optionally, you may specify a `max` object property:
  54
  55 ```json
  56 "complexity": ["error", 2]
  57 ```
  58
  59 is equivalent to
  60
  61 ```json
  62 "complexity": ["error", { "max": 2 }]
  63 ```
  64
  65 **Deprecated:** the object property `maximum` is deprecated. Please use the property `max` instead.
  66
  67 ## When Not To Use It
  68
  69 If you can't determine an appropriate complexity limit for your code, then it's best to disable this rule.
  70
  71 ## Further Reading
  72
  73 * [Cyclomatic Complexity](https://en.wikipedia.org/wiki/Cyclomatic_complexity)
  74 * [Complexity Analysis of JavaScript Code](https://ariya.io/2012/12/complexity-analysis-of-javascript-code)
  75 * [More about Complexity in JavaScript](https://craftsmanshipforsoftware.com/2015/05/25/complexity-for-javascript/)
  76 * [About Complexity](https://web.archive.org/web/20160808115119/http://jscomplexity.org/complexity)
  77 * [Discussion about Complexity in ESLint and more links](https://github.com/eslint/eslint/issues/4808#issuecomment-167795140)
  78
  79 ## Related Rules
  80
  81 * [max-depth](max-depth.md)
  82 * [max-len](max-len.md)
  83 * [max-lines](max-lines.md)
  84 * [max-lines-per-function](max-lines-per-function.md)
  85 * [max-nested-callbacks](max-nested-callbacks.md)
  86 * [max-params](max-params.md)
  87 * [max-statements](max-statements.md)