no-global-assign
Disallow assignments to native objects or read-only global variables
The "extends": "eslint:recommended" property in a configuration file enables this 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:
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.
Examples of incorrect code for this rule:
/*eslint no-global-assign: "error"*/
Object = null
undefined = 1
/*eslint no-global-assign: "error"*/
/*eslint-env browser*/
window = {}
length = 1
top = 1
/*eslint no-global-assign: "error"*/
/*global a:readonly*/
a = 1
Examples of correct code for this rule:
/*eslint no-global-assign: "error"*/
a = 1
var b = 1
b = 2
/*eslint no-global-assign: "error"*/
/*eslint-env browser*/
onload = function() {}
/*eslint no-global-assign: "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:
{
"rules": {
"no-global-assign": ["error", {"exceptions": ["Object"]}]
}
}
When Not To Use It
If you are trying to override one of the native objects.
Related Rules
Version
This rule was introduced in ESLint v3.3.0.