Setup Eslint, Prettier and Husky for a Typescript project.

Linting.md

Setup Eslint, Prettier and Husky for Typescript

Eslint

• Install eslint and plugins

yarn add -D eslint @typescript-eslint/parser @typescript-eslint/eslint-plugin

• Create a eslintrc file

yarn eslint --init

• Configure eslintrc

module.exports = {
  ...
  parser: '@typescript-eslint/parser',
  plugins: ['@typescript-eslint'],
  extends: [
    'eslint:recommended',
    'plugin:@typescript-eslint/recommended',
  ],
  parserOptions: {
    ecmaVersion: 'latest',
    sourceType: 'module',
  },
};

• Add lint script in package.json

{
 ...
 "scripts": {
    ...
    "lint": "eslint '**/*.{js,ts,tsx}' --fix --cache",
  }
}

• with React

yarn add -D eslint-plugin-react

module.exports = {
  ...
  plugins: [
    ...
    'react',
  ],
  extends: [
    ...
    'plugin:react/recommended',
  ],
};

• with React Native

yarn add -D eslint-plugin-react @react-native-community/eslint-config

module.exports = {
  ...
  plugins: [
    ...
    'react',
  ],
  extends: [
    ...
    'plugin:react/recommended',
    '@react-native-community',
  ],
};

• with NextJs (already done if you used create-next-app)

yarn add -D eslint-config-next

module.exports = {
  ...
  extends: [
    ...
    'next/core-web-vitals',
  ],
};

Prettier

• Install dependencies

yarn add -D prettier eslint-config-prettier eslint-plugin-prettier

• Create the Prettier file

touch .prettierrc

• Some basic configuration

{
  "useTabs": false,
  "trailingComma": "es5",
  "tabWidth": 2,
  "semi": true,
  "singleQuote": true,
  "printWidth": 120,
  "quoteProps": "consistent",
  "arrowParens": "avoid",
  "endOfLine": "auto"
}

• Add plugin inside eslintrc

module.exports = {
  plugins: [
    ...
    'prettier',
  ],
  extends: [
    ...
    'plugin:prettier/recommended',
  ]
};

Husky

• Install dependencies

yarn add -D husky

• Inside package.json add postinstall script

{
  ...
  "scripts": {
    ...
    "postinstall": "rm -f .husky/pre-commit && husky install && husky add .husky/pre-commit 'yarn lint'",
  }
}

This will run after the project install all the dependencies. (Or you can run yarn postinstall)

• For additional configurations edit ./husky/pre-commit.
• In order to make this work the flag -a is needed. (eg: git commit -am '...)

Bonus

Additionally I like to add some rules for eslint

module.exports = {
  ...
  rules: {
    ...
    'no-console': 'warn',
    '@typescript-eslint/no-unused-vars': 'warn',
    '@typescript-eslint/no-explicit-any': 'warn',
    'prettier/prettier': 'error', // this will change the behavior of prettier (default is error)
  },
};

For React and React Native

module.exports = {
  ...
  rules: {
    ...
    'react/react-in-jsx-scope': 'off', // is not required to be in scope anymore
  },
};