Introduction

What is TypeScript?

JavaScript is expanded upon by TypeScript, a strongly typed programming language, which adds static types. It is compatible with any JavaScript runtime and is created and maintained by Microsoft. It compiles to ordinary JavaScript.

Why Use TypeScript with Node.js?

Node.js runs on the server side and provide a runtime environment for running JavaScript code. Dynamic typing is JavaScript; TypeScript adds static typing that increases maintainability, error protection, and code quality.

TypeScript's Principal Advantages in Node.js

• Type Safety: By identifying problems early in development, it lowers runtime errors.
• Improved Code Maintainability: Managing large codebases is made simpler.
• Enhanced IDE Support: VS Code and other editors support auto-completion, refactoring, and documentation.
• Scalability: Perfect for large-scale applications that need intricate structures.

Setting Up the Development Environment

Installing Node.js and TypeScript

First, ensure you have Node.js installed:

node -v
npm -v

If not installed, download from Node.js official site.

Then, install TypeScript globally:

npm install -g typescript
tsc -v

Initializing a Node.js Project

Create a new project folder and initialize package.json:

mkdir typescript-node-app && cd typescript-node-app
npm init -y

Installing TypeScript and Dependencies

npm install --save-dev typescript

Configuring tsconfig.json

Generate a TypeScript config file:

tsc --init

Update tsconfig.json with

{
  "compilerOptions": {
    "target": "ES6",
    "module": "CommonJS",
    "outDir": "./dist",
    "rootDir": "./src",
    "strict": true
  }
}

Writing and Compiling TypeScript in Node.js

Writing and Compiling TypeScript in Node.js

Create a src folder and a index.ts file inside:

const greet = (name: string): string => {
    return `Hello, ${name}!`;
};

console.log(greet("MoheedDev"));

Compiling TypeScript to JavaScript

tsc

It generates a dist/index.js file.

Running TypeScript Files Directly

Instead of compiling manually, use ts-node:

npm install -g ts-node
ts-node src/index.ts

Using TypeScript with Express.js

Installing Express and Type Definitions:

npm install express
npm install --save-dev @types/express

Creating an Express Server in TypeScript:

import express, { Request, Response } from "express";

const app = express();
const port = 3000;

app.get("/", (req: Request, res: Response) => {
    res.send("Hello from TypeScript + Express!");
});

app.listen(port, () => {
    console.log(`Server running on http://localhost:${port}`);
});

Middleware and Request Validation with TypeScript

Using body-parser and custom middleware:

import express from "express";
import bodyParser from "body-parser";

const app = express();
app.use(bodyParser.json());

app.post("/data", (req, res) => {
    const { name }: { name: string } = req.body;
    res.send(`Received: ${name}`);
});

app.listen(3000, () => console.log("Server running on port 3000"));

TypeScript Features for Node.js Development

Type Annotations and Interfaces:

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

const user: User = { id: 1, name: "MoheedDev" };
console.log(user);

Working with Modules in TypeScript

Create utils.ts:

export const add = (a: number, b: number): number => a + b;

Use it in index.ts:

import { add } from "./utils";
console.log(add(5, 3));

Using Decorators in TypeScript:

function Log(target: any, propertyKey: string, descriptor: PropertyDescriptor) {
    console.log(`Method called: ${propertyKey}`);
}

class Example {
    @Log
    show() {
        console.log("Hello from decorator MoheedDev ");
    }
}

Debugging & Error Handling in TypeScript

Debugging TypeScript in Node.js

Use --inspect with ts-node:

node --inspect dist/index.js

Common TypeScript Errors in Node.js

• Cannot find module: Fix by ensuring tsconfig.json includes "moduleResolution": "Node".
• Type mismatch: Ensure function parameters and return values match expected types.

Error Handling Best Practices

Using try...catch:

try {
    throw new Error("Something went wrong!");
} catch (error) {
    console.error("Error:", error.message);
}

Testing a TypeScript Node.js Application

Setting Up Jest for TypeScript

npm install --save-dev jest ts-jest @types/jest

Configure jest.config.js:

module.exports = {
    preset: "ts-jest",
    testEnvironment: "node",
};

Writing Unit Tests for TypeScript Functions

const sum = (a: number, b: number): number => a + b;
export { sum };

Test case:

import { sum } from "./sum";

test("adds 1 + 2 to equal 3", () => {
    expect(sum(1, 2)).toBe(3);
});

Running Tests

npm test

Deployment & Best Practices

Using Webpack & Babel for Optimization

Install Webpack and Babel:

npm install --save-dev webpack webpack-cli babel-loader @babel/core @babel/preset-env

Update webpack.config.js:

module.exports = {
    entry: "./src/index.ts",
    output: {
        filename: "bundle.js",
        path: __dirname + "/dist",
    },
    module: {
        rules: [{ test: /\.ts$/, use: "babel-loader" }],
    },
    resolve: {
        extensions: [".ts", ".js"],
    },
};

/*Console.log"moheeddev.com"*/

How to Deploy a TypeScript-Based Node.js App

( How to Use TypeScript with Node.js (Comprehensive Technical Guide) )

• Compile TypeScript to JavaScript
• Use pm2 for process management

pm2 start dist/index.jspm2 start dist/index.js

Performance Optimization Tips

• Use async/await for efficient execution
• Enable caching for repeated operations
• Minimize dependencies

Conclusion

This guide covers everything you need to integrate TypeScript with Node.js efficiently. Implement these best practices and debugging techniques to write scalable and maintainable backend applications.

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