no-native-reassign

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:

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.

See also: Specify Globals

Examples of incorrect code for this rule:

::: incorrect

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

Object = null
undefined = 1

:::

::: incorrect

/*eslint no-native-reassign: "error"*/
/*global window:readonly*/

window = {}

:::

Examples of correct code for this rule:

::: correct

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

a = 1
var b = 1
b = 2

:::

::: correct

/*eslint no-native-reassign: "error"*/
/*global onload:writable*/

onload = function() {}

:::

Options

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

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

When Not To Use It

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