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1[![npm version](https://img.shields.io/npm/v/eslint.svg)](https://www.npmjs.com/package/eslint)
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5<br />
6[![Open Collective Backers](https://img.shields.io/opencollective/backers/eslint)](https://opencollective.com/eslint)
7[![Open Collective Sponsors](https://img.shields.io/opencollective/sponsors/eslint)](https://opencollective.com/eslint)
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9
10# ESLint
11
12[Website](https://eslint.org) |
13[Configure ESLint](https://eslint.org/docs/latest/use/configure) |
14[Rules](https://eslint.org/docs/rules/) |
15[Contribute to ESLint](https://eslint.org/docs/latest/contribute) |
16[Report Bugs](https://eslint.org/docs/latest/contribute/report-bugs) |
17[Code of Conduct](https://eslint.org/conduct) |
18[Twitter](https://twitter.com/geteslint) |
19[Discord](https://eslint.org/chat) |
20[Mastodon](https://fosstodon.org/@eslint)
21
22ESLint is a tool for identifying and reporting on patterns found in ECMAScript/JavaScript code. In many ways, it is similar to JSLint and JSHint with a few exceptions:
23
24* ESLint uses [Espree](https://github.com/eslint/espree) for JavaScript parsing.
25* ESLint uses an AST to evaluate patterns in code.
26* ESLint is completely pluggable, every single rule is a plugin and you can add more at runtime.
27
28## Table of Contents
29
301. [Installation and Usage](#installation-and-usage)
312. [Configuration](#configuration)
323. [Code of Conduct](#code-of-conduct)
334. [Filing Issues](#filing-issues)
345. [Frequently Asked Questions](#frequently-asked-questions)
356. [Releases](#releases)
367. [Security Policy](#security-policy)
378. [Semantic Versioning Policy](#semantic-versioning-policy)
389. [Stylistic Rule Updates](#stylistic-rule-updates)
3910. [License](#license)
4011. [Team](#team)
4112. [Sponsors](#sponsors)
4213. [Technology Sponsors](#technology-sponsors)
43
44## Installation and Usage
45
46Prerequisites: [Node.js](https://nodejs.org/) (`^12.22.0`, `^14.17.0`, or `>=16.0.0`) built with SSL support. (If you are using an official Node.js distribution, SSL is always built in.)
47
48You can install and configure ESLint using this command:
49
50```shell
51npm init @eslint/config
52```
53
54After that, you can run ESLint on any file or directory like this:
55
56```shell
57./node_modules/.bin/eslint yourfile.js
58```
59
60## Configuration
61
62After running `npm init @eslint/config`, you'll have an `.eslintrc` file in your directory. In it, you'll see some rules configured like this:
63
64```json
65{
66 "rules": {
67 "semi": ["error", "always"],
68 "quotes": ["error", "double"]
69 }
70}
71```
72
73The names `"semi"` and `"quotes"` are the names of [rules](https://eslint.org/docs/rules) in ESLint. The first value is the error level of the rule and can be one of these values:
74
75* `"off"` or `0` - turn the rule off
76* `"warn"` or `1` - turn the rule on as a warning (doesn't affect exit code)
77* `"error"` or `2` - turn the rule on as an error (exit code will be 1)
78
79The three error levels allow you fine-grained control over how ESLint applies rules (for more configuration options and details, see the [configuration docs](https://eslint.org/docs/latest/use/configure)).
80
81## Code of Conduct
82
83ESLint adheres to the [JS Foundation Code of Conduct](https://eslint.org/conduct).
84
85## Filing Issues
86
87Before filing an issue, please be sure to read the guidelines for what you're reporting:
88
89* [Bug Report](https://eslint.org/docs/latest/contribute/report-bugs)
90* [Propose a New Rule](https://eslint.org/docs/latest/contribute/propose-new-rule)
91* [Proposing a Rule Change](https://eslint.org/docs/latest/contribute/propose-rule-change)
92* [Request a Change](https://eslint.org/docs/latest/contribute/request-change)
93
94## Frequently Asked Questions
95
96### I'm using JSCS, should I migrate to ESLint?
97
98Yes. [JSCS has reached end of life](https://eslint.org/blog/2016/07/jscs-end-of-life) and is no longer supported.
99
100We have prepared a [migration guide](https://eslint.org/docs/latest/use/migrating-from-jscs) to help you convert your JSCS settings to an ESLint configuration.
101
102We are now at or near 100% compatibility with JSCS. If you try ESLint and believe we are not yet compatible with a JSCS rule/configuration, please create an issue (mentioning that it is a JSCS compatibility issue) and we will evaluate it as per our normal process.
103
104### Does Prettier replace ESLint?
105
106No, ESLint and Prettier have diffent jobs: ESLint is a linter (looking for problematic patterns) and Prettier is a code formatter. Using both tools is common, refer to [Prettier's documentation](https://prettier.io/docs/en/install#eslint-and-other-linters) to learn how to configure them to work well with each other.
107
108### Why can't ESLint find my plugins?
109
110* Make sure your plugins (and ESLint) are both in your project's `package.json` as devDependencies (or dependencies, if your project uses ESLint at runtime).
111* Make sure you have run `npm install` and all your dependencies are installed.
112* Make sure your plugins' peerDependencies have been installed as well. You can use `npm view eslint-plugin-myplugin peerDependencies` to see what peer dependencies `eslint-plugin-myplugin` has.
113
114### Does ESLint support JSX?
115
116Yes, ESLint natively supports parsing JSX syntax (this must be enabled in [configuration](https://eslint.org/docs/latest/use/configure)). 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://www.npmjs.com/package/eslint-plugin-react) if you are using React and want React semantics.
117
118### What ECMAScript versions does ESLint support?
119
120ESLint has full support for ECMAScript 3, 5 (default), 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022, and 2023. You can set your desired ECMAScript syntax (and other settings, like global variables or your target environments) through [configuration](https://eslint.org/docs/latest/use/configure).
121
122### What about experimental features?
123
124ESLint's parser only officially supports the latest final ECMAScript standard. We will make changes to core rules in order to avoid crashes on stage 3 ECMAScript syntax proposals (as long as they are implemented using the correct experimental ESTree syntax). We may make changes to core rules to better work with language extensions (such as JSX, Flow, and TypeScript) on a case-by-case basis.
125
126In other cases (including if rules need to warn on more or fewer cases due to new syntax, rather than just not crashing), we recommend you use other parsers and/or rule plugins. If you are using Babel, you can use [@babel/eslint-parser](https://www.npmjs.com/package/@babel/eslint-parser) and [@babel/eslint-plugin](https://www.npmjs.com/package/@babel/eslint-plugin) to use any option available in Babel.
127
128Once a language feature has been adopted into the ECMAScript standard (stage 4 according to the [TC39 process](https://tc39.github.io/process-document/)), we will accept issues and pull requests related to the new feature, subject to our [contributing guidelines](https://eslint.org/docs/latest/contribute). Until then, please use the appropriate parser and plugin(s) for your experimental feature.
129
130### Where to ask for help?
131
132Open a [discussion](https://github.com/eslint/eslint/discussions) or stop by our [Discord server](https://eslint.org/chat).
133
134### Why doesn't ESLint lock dependency versions?
135
136Lock files like `package-lock.json` are helpful for deployed applications. They ensure that dependencies are consistent between environments and across deployments.
137
138Packages like `eslint` that get published to the npm registry do not include lock files. `npm install eslint` as a user will respect version constraints in ESLint's `package.json`. ESLint and its dependencies will be included in the user's lock file if one exists, but ESLint's own lock file would not be used.
139
140We intentionally don't lock dependency versions so that we have the latest compatible dependency versions in development and CI that our users get when installing ESLint in a project.
141
142The Twilio blog has a [deeper dive](https://www.twilio.com/blog/lockfiles-nodejs) to learn more.
143
144## Releases
145
146We have scheduled releases every two weeks on Friday or Saturday. You can follow a [release issue](https://github.com/eslint/eslint/issues?q=is%3Aopen+is%3Aissue+label%3Arelease) for updates about the scheduling of any particular release.
147
148## Security Policy
149
150ESLint takes security seriously. We work hard to ensure that ESLint is safe for everyone and that security issues are addressed quickly and responsibly. Read the full [security policy](https://github.com/eslint/.github/blob/master/SECURITY.md).
151
152## Semantic Versioning Policy
153
154ESLint follows [semantic versioning](https://semver.org). However, due to the nature of ESLint as a code quality tool, it's not always clear when a minor or major version bump occurs. To help clarify this for everyone, we've defined the following semantic versioning policy for ESLint:
155
156* Patch release (intended to not break your lint build)
157 * A bug fix in a rule that results in ESLint reporting fewer linting errors.
158 * A bug fix to the CLI or core (including formatters).
159 * Improvements to documentation.
160 * Non-user-facing changes such as refactoring code, adding, deleting, or modifying tests, and increasing test coverage.
161 * Re-releasing after a failed release (i.e., publishing a release that doesn't work for anyone).
162* Minor release (might break your lint build)
163 * A bug fix in a rule that results in ESLint reporting more linting errors.
164 * A new rule is created.
165 * A new option to an existing rule that does not result in ESLint reporting more linting errors by default.
166 * A new addition to an existing rule to support a newly-added language feature (within the last 12 months) that will result in ESLint reporting more linting errors by default.
167 * An existing rule is deprecated.
168 * A new CLI capability is created.
169 * New capabilities to the public API are added (new classes, new methods, new arguments to existing methods, etc.).
170 * A new formatter is created.
171 * `eslint:recommended` is updated and will result in strictly fewer linting errors (e.g., rule removals).
172* Major release (likely to break your lint build)
173 * `eslint:recommended` is updated and may result in new linting errors (e.g., rule additions, most rule option updates).
174 * A new option to an existing rule that results in ESLint reporting more linting errors by default.
175 * An existing formatter is removed.
176 * Part of the public API is removed or changed in an incompatible way. The public API includes:
177 * Rule schemas
178 * Configuration schema
179 * Command-line options
180 * Node.js API
181 * Rule, formatter, parser, plugin APIs
182
183According to our policy, any minor update may report more linting errors than the previous release (ex: from a bug fix). As such, we recommend using the tilde (`~`) in `package.json` e.g. `"eslint": "~3.1.0"` to guarantee the results of your builds.
184
185## Stylistic Rule Updates
186
187Stylistic rules are frozen according to [our policy](https://eslint.org/blog/2020/05/changes-to-rules-policies) on how we evaluate new rules and rule changes.
188This means:
189
190* **Bug fixes**: We will still fix bugs in stylistic rules.
191* **New ECMAScript features**: We will also make sure stylistic rules are compatible with new ECMAScript features.
192* **New options**: We will **not** add any new options to stylistic rules unless an option is the only way to fix a bug or support a newly-added ECMAScript feature.
193
194## License
195
196[![FOSSA Status](https://app.fossa.io/api/projects/git%2Bhttps%3A%2F%2Fgithub.com%2Feslint%2Feslint.svg?type=large)](https://app.fossa.io/projects/git%2Bhttps%3A%2F%2Fgithub.com%2Feslint%2Feslint?ref=badge_large)
197
198## Team
199
200These folks keep the project moving and are resources for help.
201
202<!-- NOTE: This section is autogenerated. Do not manually edit.-->
203
204<!--teamstart-->
205
206### Technical Steering Committee (TSC)
207
208The people who manage releases, review feature requests, and meet regularly to ensure ESLint is properly maintained.
209
210<table><tbody><tr><td align="center" valign="top" width="11%">
211<a href="https://github.com/nzakas">
212<img src="https://github.com/nzakas.png?s=75" width="75" height="75" alt="Nicholas C. Zakas's Avatar"><br />
213Nicholas C. Zakas
214</a>
215</td><td align="center" valign="top" width="11%">
216<a href="https://github.com/mdjermanovic">
217<img src="https://github.com/mdjermanovic.png?s=75" width="75" height="75" alt="Milos Djermanovic's Avatar"><br />
218Milos Djermanovic
219</a>
220</td></tr></tbody></table>
221
222### Reviewers
223
224The people who review and implement new features.
225
226<table><tbody><tr><td align="center" valign="top" width="11%">
227<a href="https://github.com/aladdin-add">
228<img src="https://github.com/aladdin-add.png?s=75" width="75" height="75" alt="唯然's Avatar"><br />
229唯然
230</a>
231</td><td align="center" valign="top" width="11%">
232<a href="https://github.com/snitin315">
233<img src="https://github.com/snitin315.png?s=75" width="75" height="75" alt="Nitin Kumar's Avatar"><br />
234Nitin Kumar
235</a>
236</td></tr></tbody></table>
237
238### Committers
239
240The people who review and fix bugs and help triage issues.
241
242<table><tbody><tr><td align="center" valign="top" width="11%">
243<a href="https://github.com/bmish">
244<img src="https://github.com/bmish.png?s=75" width="75" height="75" alt="Bryan Mishkin's Avatar"><br />
245Bryan Mishkin
246</a>
247</td><td align="center" valign="top" width="11%">
248<a href="https://github.com/fasttime">
249<img src="https://github.com/fasttime.png?s=75" width="75" height="75" alt="Francesco Trotta's Avatar"><br />
250Francesco Trotta
251</a>
252</td><td align="center" valign="top" width="11%">
253<a href="https://github.com/ota-meshi">
254<img src="https://github.com/ota-meshi.png?s=75" width="75" height="75" alt="Yosuke Ota's Avatar"><br />
255Yosuke Ota
256</a>
257</td><td align="center" valign="top" width="11%">
258<a href="https://github.com/Tanujkanti4441">
259<img src="https://github.com/Tanujkanti4441.png?s=75" width="75" height="75" alt="Tanuj Kanti's Avatar"><br />
260Tanuj Kanti
261</a>
262</td></tr></tbody></table>
263
264### Website Team
265
266Team members who focus specifically on eslint.org
267
268<table><tbody><tr><td align="center" valign="top" width="11%">
269<a href="https://github.com/amareshsm">
270<img src="https://github.com/amareshsm.png?s=75" width="75" height="75" alt="Amaresh S M's Avatar"><br />
271Amaresh S M
272</a>
273</td><td align="center" valign="top" width="11%">
274<a href="https://github.com/harish-sethuraman">
275<img src="https://github.com/harish-sethuraman.png?s=75" width="75" height="75" alt="Strek's Avatar"><br />
276Strek
277</a>
278</td><td align="center" valign="top" width="11%">
279<a href="https://github.com/kecrily">
280<img src="https://github.com/kecrily.png?s=75" width="75" height="75" alt="Percy Ma's Avatar"><br />
281Percy Ma
282</a>
283</td></tr></tbody></table>
284
285<!--teamend-->
286
287## Sponsors
288
289The following companies, organizations, and individuals support ESLint's ongoing maintenance and development. [Become a Sponsor](https://opencollective.com/eslint) to get your logo on our README and website.
290
291<!-- NOTE: This section is autogenerated. Do not manually edit.-->
292<!--sponsorsstart-->
293<h3>Platinum Sponsors</h3>
294<p><a href="#"><img src="https://images.opencollective.com/2021-frameworks-fund/logo.png" alt="Chrome Frameworks Fund" height="undefined"></a> <a href="https://automattic.com"><img src="https://images.opencollective.com/automattic/d0ef3e1/logo.png" alt="Automattic" height="undefined"></a></p><h3>Gold Sponsors</h3>
295<p><a href="https://engineering.salesforce.com"><img src="https://images.opencollective.com/salesforce/ca8f997/logo.png" alt="Salesforce" height="96"></a> <a href="https://www.airbnb.com/"><img src="https://images.opencollective.com/airbnb/d327d66/logo.png" alt="Airbnb" height="96"></a></p><h3>Silver Sponsors</h3>
296<p><a href="https://liftoff.io/"><img src="https://images.opencollective.com/liftoff/5c4fa84/logo.png" alt="Liftoff" height="64"></a> <a href="https://americanexpress.io"><img src="https://avatars.githubusercontent.com/u/3853301?v=4" alt="American Express" height="64"></a> <a href="https://www.workleap.com"><img src="https://avatars.githubusercontent.com/u/53535748?u=d1e55d7661d724bf2281c1bfd33cb8f99fe2465f&v=4" alt="Workleap" height="64"></a></p><h3>Bronze Sponsors</h3>
297<p><a href="https://themeisle.com"><img src="https://images.opencollective.com/themeisle/d5592fe/logo.png" alt="ThemeIsle" height="32"></a> <a href="https://www.crosswordsolver.org/anagram-solver/"><img src="https://images.opencollective.com/anagram-solver/2666271/logo.png" alt="Anagram Solver" height="32"></a> <a href="https://icons8.com/"><img src="https://images.opencollective.com/icons8/7fa1641/logo.png" alt="Icons8" height="32"></a> <a href="https://discord.com"><img src="https://images.opencollective.com/discordapp/f9645d9/logo.png" alt="Discord" height="32"></a> <a href="https://transloadit.com/"><img src="https://avatars.githubusercontent.com/u/125754?v=4" alt="Transloadit" height="32"></a> <a href="https://www.ignitionapp.com"><img src="https://avatars.githubusercontent.com/u/5753491?v=4" alt="Ignition" height="32"></a> <a href="https://nx.dev"><img src="https://avatars.githubusercontent.com/u/23692104?v=4" alt="Nx" height="32"></a> <a href="https://herocoders.com"><img src="https://avatars.githubusercontent.com/u/37549774?v=4" alt="HeroCoders" height="32"></a></p>
298<!--sponsorsend-->
299
300## Technology Sponsors
301
302* Site search ([eslint.org](https://eslint.org)) is sponsored by [Algolia](https://www.algolia.com)
303* Hosting for ([eslint.org](https://eslint.org)) is sponsored by [Netlify](https://www.netlify.com)
304* Password management is sponsored by [1Password](https://www.1password.com)