Yasinskyi Ivan's blog

How to add ESlint to javascript or node project

Yasinskyi Ivan's photo
Yasinskyi Ivan
·

2 min read

ESlint is the best tool that we can use to ensure a consistent code style. In this article, you will learn how to add and set up elsint on your nodejs or javascript project.

First of all, install ESlint using npm:

npm install eslint

To set up ESlint, we should run the command below:

npm init @eslint/config

And choose:

To check syntax, find problems, and enforce code style.

CommonJS (require/exports)

None of these

If you don't use TypeScript yet :) choose No, if use choose Yes.

Choose Node

I recommend you choose: Use a popular style guide.

Choose Standard:

I recommend choosing Javascript but be free to choose whatever you want:

Choose Yes:

I choose npm here:

When the installation is complete, you will see .eslintrc.js file at the root of your project.

If you are using jest, please install ESlint for jest:

npm i eslint-plugin-jest

Then, add lint and lint-fix command to the scripts section in the package.json file:

{
  "name": "nodejs_app",
  "version": "0.0.1",
  "description": "",
  "main": "index.js",
  "jest": {
    "clearMocks": true,
    "roots": [
      "__tests__"
    ],
    "setupFiles": [
      "<rootDir>/jest.setup.js"
    ],
    "verbose": true
  },
  "scripts": {
    "lint": "./node_modules/.bin/eslint .",
    "lint-fix": "./node_modules/.bin/eslint --fix",
    "test": "./node_modules/.bin/jest -i"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "eslint": "^8.19.0",
    "eslint-config-standard": "^17.0.0",
    "eslint-plugin-import": "^2.26.0",
    "eslint-plugin-n": "^15.2.3",
    "eslint-plugin-promise": "^6.0.0",
    "jest": "^28.1.1"
  },
  "dependencies": {
    "eslint-plugin-jest": "^26.5.3"
  }
}

Finally, make sure that your .eslintrc.js file looks like this:

module.exports = {
  env: {
    browser: true,
    commonjs: true,
    es2021: true,
    'jest/globals': true
  },
  extends: [
    'standard'
  ],
  parserOptions: {
    ecmaVersion: 'latest'
  },
  plugins: ['jest'],
  rules: {
    'jest/no-disabled-tests': 'warn',
    'jest/no-focused-tests': 'error',
    'jest/no-identical-title': 'error',
    'jest/prefer-to-have-length': 'warn',
    'jest/valid-expect': 'error'
  }
}

Now you can run ESlint from the root folder of your project:

npm run lint
eslint