Linting and formatting are essential practices in software development that help maintain code quality and consistency. In this section, we will explore how to set up and use linting and formatting tools in TypeScript projects.

Linting is the process of running a program that analyzes your code for potential errors. A linter can help you catch common mistakes, enforce coding standards, and improve code quality.

• Error Detection: Identifies syntax errors, potential bugs, and problematic patterns.
• Code Consistency: Enforces a consistent coding style across the project.
• Improved Readability: Makes code easier to read and maintain.

ESLint is a popular linting tool for JavaScript and TypeScript. To set up ESLint in a TypeScript project, follow these steps:

First, install ESLint and the TypeScript ESLint plugin using npm:

Create a .eslintrc.json file in the root of your project and add the following configuration:

Add a script to your package.json to run ESLint:

Run the linting script to analyze your TypeScript files:

Prettier is a code formatter that enforces a consistent style by parsing your code and re-printing it with its own rules.

• Consistent Style: Ensures a uniform code style across the project.
• Automatic Formatting: Automatically formats code on save or commit.
• Integration with Editors: Easily integrates with popular code editors.

Install Prettier using npm:

Create a .prettierrc file in the root of your project and add your preferred configuration:

Add a script to your package.json to run Prettier:

Run the formatting script to format your TypeScript files:

To avoid conflicts between ESLint and Prettier, you can use the eslint-config-prettier package to disable ESLint rules that might conflict with Prettier.

Install the package using npm:

Update your .eslintrc.json to include prettier in the extends array:

1. Install ESLint and Prettier: Follow the steps above to install and configure ESLint and Prettier in a new TypeScript project.
2. Create a TypeScript File: Create a src/index.ts file with the following content:

   const greeting: string = "Hello, World!";
   console.log(greeting);
   

3. Run ESLint: Run the ESLint script to check for linting errors.
4. Run Prettier: Run the Prettier script to format the code.

1. Install ESLint and Prettier:

   npm install eslint @typescript-eslint/parser @typescript-eslint/eslint-plugin prettier eslint-config-prettier --save-dev
   

2. Create Configuration Files:

   • .eslintrc.json:

     {
       "parser": "@typescript-eslint/parser",
       "parserOptions": {
         "ecmaVersion": 2020,
         "sourceType": "module"
       },
       "plugins": ["@typescript-eslint"],
       "extends": [
         "eslint:recommended",
         "plugin:@typescript-eslint/recommended",
         "prettier"
       ],
       "rules": {
         // Add custom rules here
       }
     }
     

   • .prettierrc:

     {
       "semi": true,
       "singleQuote": true,
       "trailingComma": "all",
       "printWidth": 80
     }
     

3. Add Scripts to package.json:

   "scripts": {
     "lint": "eslint 'src/**/*.{ts,tsx}'",
     "format": "prettier --write 'src/**/*.{ts,tsx}'"
   }
   

4. Run ESLint and Prettier:

   npm run lint
   npm run format
   

In this section, we covered the importance of linting and formatting in maintaining code quality and consistency. We learned how to set up and use ESLint and Prettier in a TypeScript project, and how to integrate them to avoid conflicts. By following these practices, you can ensure that your codebase remains clean, readable, and maintainable.