eslint/docs/rules/max-classes-per-file.md

   1 # enforce a maximum number of classes per file (max-classes-per-file)
   2
   3 Files containing multiple classes can often result in a less navigable
   4 and poorly structured codebase. Best practice is to keep each file
   5 limited to a single responsibility.
   6
   7 ## Rule Details
   8
   9 This rule enforces that each file may contain only a particular number
  10 of classes and no more.
  11
  12 Examples of **incorrect** code for this rule:
  13
  14 ```js
  15 /*eslint max-classes-per-file: "error"*/
  16
  17 class Foo {}
  18 class Bar {}
  19 ```
  20
  21 Examples of **correct** code for this rule:
  22
  23 ```js
  24 /*eslint max-classes-per-file: "error"*/
  25
  26 class Foo {}
  27 ```
  28
  29 ## Options
  30
  31 This rule may be configured with either an object or a number.
  32
  33 If the option is an object, it may contain one or both of:
  34
  35 -   `ignoreExpressions`: a boolean option (defaulted to `false`) to ignore class expressions.
  36 -   `max`: a numeric option (defaulted to 1) to specify the maximum number of classes.
  37
  38 For example:
  39
  40 ```json
  41 {
  42     "max-classes-per-file": ["error", 1]
  43 }
  44 ```
  45
  46 ```json
  47 {
  48     "max-classes-per-file": [
  49         "error",
  50         { "ignoreExpressions": true, "max": 2 }
  51     ]
  52 }
  53 ```
  54
  55 Examples of **correct** code for this rule with the `max` option set to `2`:
  56
  57 ```js
  58 /* eslint max-classes-per-file: ["error", 2] */
  59
  60 class Foo {}
  61 class Bar {}
  62 ```
  63
  64 Examples of **correct** code for this rule with the `ignoreExpressions` option set to `true`:
  65
  66 ```js
  67 /* eslint max-classes-per-file: ["error", { ignoreExpressions: true }] */
  68
  69 class VisitorFactory {
  70     forDescriptor(descriptor) {
  71         return class {
  72             visit(node) {
  73                 return `Visiting ${descriptor}.`;
  74             }
  75         };
  76     }
  77 }
  78 ```