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docs: update with "Specifying Parser Options" #17435

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merged 4 commits into from Aug 2, 2023
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docs: update with "Specifying Parser Options" #17435

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docs: update with "Specifying Parser Options"
Ryan-Dia Jul 31, 2023
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docs : reapply lint
Ryan-Dia Jul 31, 2023
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Update docs/src/use/configure/language-options.md
fasttime Jul 31, 2023
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docs : reapply lint
Ryan-Dia Aug 1, 2023
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89 changes: 44 additions & 45 deletions docs/src/use/configure/language-options.md
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Expand Up @@ -5,7 +5,6 @@ eleventyNavigation:
parent: configure
title: Configure Language Options
order: 3

---

The JavaScript ecosystem has a variety of runtimes, versions, extensions, and frameworks. Each of these can have different supported syntax and global variables. ESLint lets you configure language options specific to the JavaScript used in your project, like custom global variables. You can also use plugins to extend ESLint to support your project's language options.
Expand All @@ -14,40 +13,40 @@ The JavaScript ecosystem has a variety of runtimes, versions, extensions, and fr

An environment provides predefined global variables. The available environments are:

* `browser` - browser global variables.
* `node` - Node.js global variables and Node.js scoping.
* `commonjs` - CommonJS global variables and CommonJS scoping (use this for browser-only code that uses Browserify/WebPack).
* `shared-node-browser` - Globals common to both Node.js and Browser.
* `es6` - enable all ECMAScript 6 features except for modules (this automatically sets the `ecmaVersion` parser option to 6).
* `es2016` - adds all ECMAScript 2016 globals and automatically sets the `ecmaVersion` parser option to 7.
* `es2017` - adds all ECMAScript 2017 globals and automatically sets the `ecmaVersion` parser option to 8.
* `es2018` - adds all ECMAScript 2018 globals and automatically sets the `ecmaVersion` parser option to 9.
* `es2019` - adds all ECMAScript 2019 globals and automatically sets the `ecmaVersion` parser option to 10.
* `es2020` - adds all ECMAScript 2020 globals and automatically sets the `ecmaVersion` parser option to 11.
* `es2021` - adds all ECMAScript 2021 globals and automatically sets the `ecmaVersion` parser option to 12.
* `es2022` - adds all ECMAScript 2022 globals and automatically sets the `ecmaVersion` parser option to 13.
* `es2023` - adds all ECMAScript 2023 globals and automatically sets the `ecmaVersion` parser option to 14.
* `es2024` - adds all ECMAScript 2024 globals and automatically sets the `ecmaVersion` parser option to 15.
* `worker` - web workers global variables.
* `amd` - defines `require()` and `define()` as global variables as per the [amd](https://github.com/amdjs/amdjs-api/blob/master/AMD.md) spec.
* `mocha` - adds all of the Mocha testing global variables.
* `jasmine` - adds all of the Jasmine testing global variables for version 1.3 and 2.0.
* `jest` - Jest global variables.
* `phantomjs` - PhantomJS global variables.
* `protractor` - Protractor global variables.
* `qunit` - QUnit global variables.
* `jquery` - jQuery global variables.
* `prototypejs` - Prototype.js global variables.
* `shelljs` - ShellJS global variables.
* `meteor` - Meteor global variables.
* `mongo` - MongoDB global variables.
* `applescript` - AppleScript global variables.
* `nashorn` - Java 8 Nashorn global variables.
* `serviceworker` - Service Worker global variables.
* `atomtest` - Atom test helper globals.
* `embertest` - Ember test helper globals.
* `webextensions` - WebExtensions globals.
* `greasemonkey` - GreaseMonkey globals.
* `browser` - browser global variables.
* `node` - Node.js global variables and Node.js scoping.
* `commonjs` - CommonJS global variables and CommonJS scoping (use this for browser-only code that uses Browserify/WebPack).
* `shared-node-browser` - Globals common to both Node.js and Browser.
* `es6` - enable all ECMAScript 6 features except for modules (this automatically sets the `ecmaVersion` parser option to 6).
* `es2016` - adds all ECMAScript 2016 globals and automatically sets the `ecmaVersion` parser option to 7.
* `es2017` - adds all ECMAScript 2017 globals and automatically sets the `ecmaVersion` parser option to 8.
* `es2018` - adds all ECMAScript 2018 globals and automatically sets the `ecmaVersion` parser option to 9.
* `es2019` - adds all ECMAScript 2019 globals and automatically sets the `ecmaVersion` parser option to 10.
* `es2020` - adds all ECMAScript 2020 globals and automatically sets the `ecmaVersion` parser option to 11.
* `es2021` - adds all ECMAScript 2021 globals and automatically sets the `ecmaVersion` parser option to 12.
* `es2022` - adds all ECMAScript 2022 globals and automatically sets the `ecmaVersion` parser option to 13.
* `es2023` - adds all ECMAScript 2023 globals and automatically sets the `ecmaVersion` parser option to 14.
* `es2024` - adds all ECMAScript 2024 globals and automatically sets the `ecmaVersion` parser option to 15.
* `worker` - web workers global variables.
* `amd` - defines `require()` and `define()` as global variables as per the [amd](https://github.com/amdjs/amdjs-api/blob/master/AMD.md) spec.
* `mocha` - adds all of the Mocha testing global variables.
* `jasmine` - adds all of the Jasmine testing global variables for version 1.3 and 2.0.
* `jest` - Jest global variables.
* `phantomjs` - PhantomJS global variables.
* `protractor` - Protractor global variables.
* `qunit` - QUnit global variables.
* `jquery` - jQuery global variables.
* `prototypejs` - Prototype.js global variables.
* `shelljs` - ShellJS global variables.
* `meteor` - Meteor global variables.
* `mongo` - MongoDB global variables.
* `applescript` - AppleScript global variables.
* `nashorn` - Java 8 Nashorn global variables.
* `serviceworker` - Service Worker global variables.
* `atomtest` - Atom test helper globals.
* `embertest` - Ember test helper globals.
* `webextensions` - WebExtensions globals.
* `greasemonkey` - GreaseMonkey globals.

These environments are not mutually exclusive, so you can define more than one at a time.

Expand Down Expand Up @@ -95,7 +94,7 @@ And in YAML:

```yaml
---
env:
env:
browser: true
node: true
```
Expand Down Expand Up @@ -163,7 +162,7 @@ And in YAML:

```yaml
---
globals:
globals:
var1: writable
var2: readonly
```
Expand Down Expand Up @@ -191,17 +190,17 @@ ESLint allows you to specify the JavaScript language options you want to support

Please note that supporting JSX syntax is not the same as supporting React. React applies specific semantics to JSX syntax that ESLint doesn't recognize. We recommend using [eslint-plugin-react](https://github.com/jsx-eslint/eslint-plugin-react) if you are using React.

By the same token, supporting ES6 syntax is not the same as supporting new ES6 globals (e.g., new types such as `Set`). For ES6 syntax, use `{ "parserOptions": { "ecmaVersion": 6 } }`; for new ES6 global variables, use `{ "env": { "es6": true } }`. Setting `{ "env": { "es6": true } }` enables ES6 syntax automatically, but `{ "parserOptions": { "ecmaVersion": 6 } }` does not enable ES6 globals automatically.
By the same token, supporting ES6 syntax is not the same as supporting new ES6 globals (e.g., new types such as `Set`). For ES6 syntax, use `{ "parserOptions": { "ecmaVersion": 6 } }`; for new ES6 global variables, use `{ "env": { "es6": true } }`. Setting `{ "env": { "es6": true } }` enables ES6 syntax automatically, but `{ "parserOptions": { "ecmaVersion": 6 } }` does not enable ES6 globals automatically. In summary, to support only ES6 syntax, use `{ "parserOptions": { "ecmaVersion": 6 } }`, and to support both ES6 syntax and new ES6 global variables, such as Set and others, use `{ "env": { "es6": true } }`.
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Parser options are set in your `.eslintrc.*` file with the `parserOptions` property. The available options are:

* `ecmaVersion` - set to 3, 5 (default), 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 to specify the version of ECMAScript syntax you want to use. You can also set it to 2015 (same as 6), 2016 (same as 7), 2017 (same as 8), 2018 (same as 9), 2019 (same as 10), 2020 (same as 11), 2021 (same as 12), 2022 (same as 13), 2023 (same as 14), or 2024 (same as 15) to use the year-based naming. You can also set `"latest"` to use the most recently supported version.
* `sourceType` - set to `"script"` (default) or `"module"` if your code is in ECMAScript modules.
* `allowReserved` - allow the use of reserved words as identifiers (if `ecmaVersion` is 3).
* `ecmaFeatures` - an object indicating which additional language features you'd like to use:
* `globalReturn` - allow `return` statements in the global scope
* `impliedStrict` - enable global [strict mode](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode) (if `ecmaVersion` is 5 or greater)
* `jsx` - enable [JSX](https://facebook.github.io/jsx/)
* `ecmaVersion` - set to 3, 5 (default), 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 to specify the version of ECMAScript syntax you want to use. You can also set it to 2015 (same as 6), 2016 (same as 7), 2017 (same as 8), 2018 (same as 9), 2019 (same as 10), 2020 (same as 11), 2021 (same as 12), 2022 (same as 13), 2023 (same as 14), or 2024 (same as 15) to use the year-based naming. You can also set `"latest"` to use the most recently supported version.
* `sourceType` - set to `"script"` (default) or `"module"` if your code is in ECMAScript modules.
* `allowReserved` - allow the use of reserved words as identifiers (if `ecmaVersion` is 3).
* `ecmaFeatures` - an object indicating which additional language features you'd like to use:
* `globalReturn` - allow `return` statements in the global scope
* `impliedStrict` - enable global [strict mode](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode) (if `ecmaVersion` is 5 or greater)
* `jsx` - enable [JSX](https://facebook.github.io/jsx/)

Here's an example `.eslintrc.json` file:

Expand Down