eslint/docs/src/user-guide/getting-started.md

   1 ---
   2 title: Getting Started with ESLint
   3 layout: doc
   4 eleventyNavigation:
   5     key: getting started
   6     parent: user guide
   7     title: Getting Started
   8     order: 1
   9
  10 ---
  11
  12 ESLint is a tool for identifying and reporting on patterns found in ECMAScript/JavaScript code, with the goal of making code more consistent and avoiding bugs. In many ways, it is similar to JSLint and JSHint with a few exceptions:
  13
  14 * ESLint uses [Espree](https://github.com/eslint/espree) for JavaScript parsing.
  15 * ESLint uses an AST to evaluate patterns in code.
  16 * ESLint is completely pluggable, every single rule is a plugin and you can add more at runtime.
  17
  18 ## Installation and Usage
  19
  20 Prerequisites: [Node.js](https://nodejs.org/en/) (`^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.)
  21
  22 You can install and configure ESLint using this command:
  23
  24 ```shell
  25 npm init @eslint/config
  26 ```
  27
  28 **Note:** `npm init @eslint/config` assumes you have a `package.json` file already. If you don't, make sure to run `npm init` or `yarn init` beforehand.
  29
  30 After that, you can run ESLint on any file or directory like this:
  31
  32 ```shell
  33 npx eslint yourfile.js
  34
  35 # or
  36
  37 yarn run eslint yourfile.js
  38 ```
  39
  40 It is also possible to install ESLint globally rather than locally (using `npm install eslint --global`). However, this is not recommended, and any plugins or shareable configs that you use must be installed locally in either case.
  41
  42 ## Configuration
  43
  44 **Note:** If you are coming from a version before 1.0.0 please see the [migration guide](migrating-to-1.0.0).
  45
  46 After running `npm init @eslint/config`, you'll have a `.eslintrc.{js,yml,json}` file in your directory. In it, you'll see some rules configured like this:
  47
  48 ```json
  49 {
  50     "rules": {
  51         "semi": ["error", "always"],
  52         "quotes": ["error", "double"]
  53     }
  54 }
  55 ```
  56
  57 The names `"semi"` and `"quotes"` are the names of [rules](/docs/rules) in ESLint. The first value is the error level of the rule and can be one of these values:
  58
  59 * `"off"` or `0` - turn the rule off
  60 * `"warn"` or `1` - turn the rule on as a warning (doesn't affect exit code)
  61 * `"error"` or `2` - turn the rule on as an error (exit code will be 1)
  62
  63 The three error levels allow you fine-grained control over how ESLint applies rules (for more configuration options and details, see the [configuration docs](configuring/)).
  64
  65 Your `.eslintrc.{js,yml,json}` configuration file will also include the line:
  66
  67 ```json
  68 {
  69     "extends": "eslint:recommended"
  70 }
  71 ```
  72
  73 Because of this line, all of the rules marked "(recommended)" on the [rules page](/docs/rules) will be turned on.  Alternatively, you can use configurations that others have created by searching for "eslint-config" on [npmjs.com](https://www.npmjs.com/search?q=eslint-config).  ESLint will not lint your code unless you extend from a shared configuration or explicitly turn rules on in your configuration.
  74
  75 ---
  76
  77 ## Next Steps
  78
  79 * Learn about [advanced configuration](configuring/) of ESLint.
  80 * Get familiar with the [command line options](command-line-interface).
  81 * Explore [ESLint integrations](integrations) into other tools like editors, build systems, and more.
  82 * Can't find just the right rule?  Make your own [custom rule](/docs/developer-guide/working-with-rules).
  83 * Make ESLint even better by [contributing](/docs/developer-guide/contributing/).