Day 66

Code Quality & ESLint

10 min

JavaScript 100 Days

Code quality tools automatically bugs dhundti hain aur consistent code style enforce karti hain. ESLint errors catch karta hai, Prettier formatting fix karta hai — professional teams ye dono use karti hain.

ESLint Setup

ESLint install aur configure karo.

.eslintrc.json

json

// npm install --save-dev eslint
// npx eslint --init

{
  "env": {
    "browser": true,
    "es2021": true,
    "node": true
  },
  "extends": ["eslint:recommended"],
  "parserOptions": {
    "ecmaVersion": "latest",
    "sourceType": "module"
  },
  "rules": {
    "no-unused-vars": "error",
    "no-console": "warn",
    "eqeqeq": "error",
    "prefer-const": "error",
    "no-var": "error",
    "arrow-parens": ["error", "always"],
    "semi": ["error", "always"]
  }
}

Prettier Config

Auto-formatting setup.

.prettierrc

json

// npm install --save-dev prettier
{
  "semi": true,
  "singleQuote": false,
  "tabWidth": 2,
  "trailingComma": "es5",
  "printWidth": 80,
  "bracketSpacing": true,
  "arrowParens": "always"
}

// package.json scripts:
// "lint": "eslint src/**/*.js"
// "format": "prettier --write src/**/*.js"
// "lint:fix": "eslint src/**/*.js --fix"

🎯 Practice Challenge

Apne kisi purane project mein ESLint aur Prettier setup karo. Saare lint errors fix karo.

TDD ApproachTypeScript Basics