best-practices-nodejs

Best Practices for TypeScript in Node.js:

Use TypeScript’s Node Definitions:

Install the @types/node package to your Node.js project to get TypeScript definitions. This gives you type checking and autocomplete for Node.js APIs.

Code Example:
```
npm install --save-dev @types/node
```

Configure tsconfig.json Properly:

The tsconfig.json file is where you set TypeScript options. For Node.js, you typically use CommonJS modules and target the version of ECMAScript supported by your Node.js environment.

Code Example:

{
  "compilerOptions": {
    "module": "commonjs",
    "target": "es2019",
    // ... other options
  }
}

Keep TypeScript Updated:

Using the latest TypeScript version means you have the newest features and the best type safety. Update regularly to keep your project current.

Code Example:

npm install typescript@latest --save-dev

Leverage Path Aliases:

Path aliases let you create shortcuts for imports. This can make your import statements shorter and easier to manage, especially in large projects.

Code Example:

{
  "compilerOptions": {
    "baseUrl": "./", // This must be specified if "paths" is.
    "paths": {
      "@models/*": ["src/models/*"],
      "@utils/*": ["src/utils/*"]
    }
  }
}

Implement Interface Segregation:

The Interface Segregation Principle suggests that no client should be forced to depend on methods it does not use. Split large interfaces into smaller, more specific ones.

Code Example:

interface User {
  id: number;
  name: string;
}

interface UserManager {
  createUser(user: User): void;
  deleteUser(userId: number): void;
}

// Instead of one large interface, we have two focused ones.

Avoid any and unknown Unless Necessary:

Use specific types instead of any or unknown whenever possible. This helps TypeScript protect you with its static typing.

Code Example:

function getItem(id: number): unknown {
  // Some logic to return an item
}

// 'unknown' is safer than 'any', but you should still try to avoid it by specifying a more specific type.

Use TypeScript’s Strict Mode:

Strict mode makes type checking tougher and can reveal potential issues sooner. Turn it on in your TypeScript configuration for better type safety.

Code Example:

{
  "compilerOptions": {
    "strict": true,
    // ... other options
  }
}

Type Third-Party Modules:

For third-party modules, use type definitions from DefinitelyTyped. If the types you need don't exist, consider adding them to DefinitelyTyped to help others.

Code Example:
```
npm install @types/express --save-dev
```

Create Custom Types for Complex Objects:

When you're working with complex objects, especially those used for configuration or environment variables, define custom types to provide clear expectations and improve safety.

Code Example:

type ServerConfig = {
  port: number;
  hostname: string;
  protocol: 'http' | 'https';
};

Type Error Handling:

In your try/catch blocks, you can type the error to better handle different kinds of errors.

Code Example:

try {
  // some operation that may fail
} catch (error: unknown) {
  if (error instanceof MyCustomError) {
    // handle custom error
  }
}

Use ts-node for Development:

ts-node allows you to run TypeScript files directly without precompiling them, which can speed up development.

Code Example:
```
npx ts-node src/index.ts
```

Optimize the Build Process:

Enable the incremental option in your tsconfig.json to speed up your build process by only recompiling files that have changed.

Code Example:

{
  "compilerOptions": {
    "incremental": true,
    // ... other options
  }
}

Use Promises and Async/Await:

Instead of callbacks, use async/await for cleaner, more readable asynchronous code.

Code Example:

async function fetchData() {
  const data = await fetch('https://api.example.com/data');
  // more code to process data
}

Apply TSLint or ESLint:

Use ESLint with TypeScript for static code analysis to catch common mistakes and enforce coding standards.

Code Example:

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

Type Guarding:

Type guards allow you to ensure that a variable is of a certain type within a specific block of code.

Code Example:

function isString(value: unknown): value is string {
  return typeof value === 'string';
}

if (isString(myVar)) {
  console.log(myVar.toUpperCase()); // safe to use string methods
}