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no-param-reassign should not throw error when using Object destructuring on parameters

See original GitHub issue

Tell us about your environment

  • ESLint Version: 5.9.0
  • Node Version: v8.11.3
  • npm Version: 5.6.0

What parser (default, Babel-ESLint, etc.) are you using? default

Please show your full configuration:

  "parserOptions": {
    "ecmaVersion": 2018,
    "sourceType": "module"
  "rules": {
    "no-param-reassign": [
        "props": true

What did you do? Please include the actual source code causing the issue, as well as the command that you used to run ESLint.

const obj = { key: [1, 2, 3] };

function foo({ key }) {
  key = [4, 5, 6];
  return key;

function bar(qux) {
  let { key } = qux;
  key = [4, 5, 6];
  return key;
node_modules/eslint/bin/eslint.js demo.js

What did you expect to happen? 0 error

What actually happened? Please include the actual, raw output from ESLint. 4:3 error Assignment to function parameter 'key' no-param-reassign

Issue Analytics

  • State:closed
  • Created 5 years ago
  • Reactions:1
  • Comments:8 (3 by maintainers)

github_iconTop GitHub Comments

platinumazurecommented, Apr 14, 2019

@pantoninho Possible misreading on my part:

I might be wrong but when we use object destructuring on the arguments, we are creating mutable local variables that point to the value of the object property of the same name.

Guess I took that out of context and read that as an assertion about the leakage of assignments to an object property “through” an assignment to a destructured value. My mistake.

In any case, I still recommend creating a new issue, so that you can provide full context for your use case.

pantoninhocommented, Apr 14, 2019

@platinumazure I can understand why it was easy to misread, sorry.

I will follow your advice. Thanks

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