JS.BASE.NO.NATIVE.REASSIGN

Disallow assignments to native objects or read-only global variables

This rule was deprecated in ESLint v3.3.0 and replaced by the no-global-assign rule.

JavaScript environments contain a number of built-in global variables, such as window in browsers and process in Node.js. In almost all cases, you don't want to assign a value to these global variables as doing so could result in losing access to important functionality. For example, you probably don't want to do this in browser code:

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window = {};

While examples such as window are obvious, there are often hundreds of built-in global objects provided by JavaScript environments. It can be hard to know if you're assigning to a global variable or not.

Rule Details

This rule disallows modifications to read-only global variables.

ESLint has the capability to configure global variables as read-only.

  • Specifying Environments
  • Specifying Globals

Examples of incorrect code for this rule:

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/*eslint no-native-reassign: "error"*/

Object = null
undefined = 1
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/*eslint no-native-reassign: "error"*/
/*eslint-env browser*/

window = {}
length = 1
top = 1
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/*eslint no-native-reassign: "error"*/
/*global a:readonly*/

a = 1

Examples of correct code for this rule:

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/*eslint no-native-reassign: "error"*/

a = 1
var b = 1
b = 2
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/*eslint no-native-reassign: "error"*/
/*eslint-env browser*/

onload = function() {}
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/*eslint no-native-reassign: "error"*/
/*global a:writable*/

a = 1

Options

This rule accepts an exceptions option, which can be used to specify a list of builtins for which reassignments will be allowed:

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{
    "rules": {
        "no-native-reassign": ["error", {"exceptions": ["Object"]}]
    }
}

When Not To Use It

If you are trying to override one of the native objects.

The content on this page is adapted from the ESLint User Guide. Copyright © OpenJS Foundation and other contributors, www.openjsf.org. All rights reserved. https://eslint.org/docs/rules/