eslint/docs/src/rules/no-constructor-return.md

   1 ---
   2 title: no-constructor-return
   3 layout: doc
   4 rule_type: problem
   5 ---
   6
   7
   8 In JavaScript, returning a value in the constructor of a class may be a mistake. Forbidding this pattern prevents mistakes resulting from unfamiliarity with the language or a copy-paste error.
   9
  10 ## Rule Details
  11
  12 This rule disallows return statements in the constructor of a class. Note that returning nothing with flow control is allowed.
  13
  14 Examples of **incorrect** code for this rule:
  15
  16 ::: incorrect
  17
  18 ```js
  19 /*eslint no-constructor-return: "error"*/
  20
  21 class A {
  22     constructor(a) {
  23         this.a = a;
  24         return a;
  25     }
  26 }
  27
  28 class B {
  29     constructor(f) {
  30         if (!f) {
  31             return 'falsy';
  32         }
  33     }
  34 }
  35 ```
  36
  37 :::
  38
  39 Examples of **correct** code for this rule:
  40
  41 ::: correct
  42
  43 ```js
  44 /*eslint no-constructor-return: "error"*/
  45
  46 class C {
  47     constructor(c) {
  48         this.c = c;
  49     }
  50 }
  51
  52 class D {
  53     constructor(f) {
  54         if (!f) {
  55             return;  // Flow control.
  56         }
  57
  58         f();
  59     }
  60 }
  61 ```
  62
  63 :::