eslint/docs/src/rules/no-dupe-args.md

   1 ---
   2 title: no-dupe-args
   3 rule_type: problem
   4 ---
   5
   6
   7
   8 If more than one parameter has the same name in a function definition, the last occurrence "shadows" the preceding occurrences. A duplicated name might be a typing error.
   9
  10 ## Rule Details
  11
  12 This rule disallows duplicate parameter names in function declarations or expressions. It does not apply to arrow functions or class methods, because the parser reports the error.
  13
  14 If ESLint parses code in strict mode, the parser (instead of this rule) reports the error.
  15
  16 Examples of **incorrect** code for this rule:
  17
  18 ::: incorrect
  19
  20 ```js
  21 /*eslint no-dupe-args: "error"*/
  22
  23 function foo(a, b, a) {
  24     console.log("value of the second a:", a);
  25 }
  26
  27 var bar = function (a, b, a) {
  28     console.log("value of the second a:", a);
  29 };
  30 ```
  31
  32 :::
  33
  34 Examples of **correct** code for this rule:
  35
  36 ::: correct
  37
  38 ```js
  39 /*eslint no-dupe-args: "error"*/
  40
  41 function foo(a, b, c) {
  42     console.log(a, b, c);
  43 }
  44
  45 var bar = function (a, b, c) {
  46     console.log(a, b, c);
  47 };
  48 ```
  49
  50 :::