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eb39fafa4f
includes a (minimal) working wrapper Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
90 lines
2.0 KiB
Markdown
90 lines
2.0 KiB
Markdown
# Disallow assignment to native objects or read-only global variables (no-global-assign)
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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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```js
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window = {};
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```
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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.
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## Rule Details
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This rule disallows modifications to read-only global variables.
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ESLint has the capability to configure global variables as read-only.
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* [Specifying Environments](../user-guide/configuring#specifying-environments)
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* [Specifying Globals](../user-guide/configuring#specifying-globals)
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Examples of **incorrect** code for this rule:
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```js
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/*eslint no-global-assign: "error"*/
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Object = null
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undefined = 1
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```
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```js
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/*eslint no-global-assign: "error"*/
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/*eslint-env browser*/
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window = {}
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length = 1
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top = 1
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```
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```js
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/*eslint no-global-assign: "error"*/
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/*global a:readonly*/
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a = 1
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```
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Examples of **correct** code for this rule:
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```js
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/*eslint no-global-assign: "error"*/
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a = 1
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var b = 1
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b = 2
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```
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```js
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/*eslint no-global-assign: "error"*/
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/*eslint-env browser*/
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onload = function() {}
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```
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```js
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/*eslint no-global-assign: "error"*/
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/*global a:writable*/
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a = 1
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```
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## Options
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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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```json
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{
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"rules": {
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"no-global-assign": ["error", {"exceptions": ["Object"]}]
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}
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}
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```
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## When Not To Use It
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If you are trying to override one of the native objects.
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## Related Rules
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* [no-extend-native](no-extend-native.md)
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* [no-redeclare](no-redeclare.md)
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* [no-shadow](no-shadow.md)
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