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Tutorial 1: TypeScript — Why & setup (tsconfig, compiler options)

  • Difficulty: Beginner
  • Description: Ever written JavaScript code that failed at runtime because of a simple typo? Discover TypeScript, a "superset" of JavaScript that adds a powerful type system to catch errors before you run your code. We'll cover why it's a game-changer and how to get it set up. 🚀
  • Time to Read: 12 minutes

Content

Why TypeScript?

TypeScript (TS) is an open-source language developed by Microsoft. It's not a completely new language; it's JavaScript with static types. All valid JavaScript code is also valid TypeScript code. TS adds an extra layer on top that helps you write more robust, scalable, and maintainable applications.

The Core Benefit: Static Type Checking

In plain JavaScript (a dynamically typed language), you can do this:

JavaScript


let myVariable = "hello";
myVariable = 42; // No error here... yet.
console.log(myVariable.toUpperCase()); // CRASH! 💥 myVariable is a number

The error above only happens when you run the code. TypeScript's static type checker catches this error in your editor as you type.

TypeScript


let myVariable: string = "hello";
myVariable = 42; // ERROR: Type 'number' is not assignable to type 'string'.

This immediate feedback loop saves countless hours of debugging.

Other benefits include:

  • Better Tooling & Autocomplete: Your code editor understands your code better, providing smarter suggestions.
  • Improved Readability: Type annotations serve as a form of documentation.
  • Easier Refactoring: The compiler helps you find all references that need to be changed.
Setting Up Your First Project

You'll need Node.js and npm installed.

1. Install the TypeScript Compiler You can install it globally to use the tsc (TypeScript Compiler) command anywhere:

Bash


npm install -g typescript

Or, more commonly, install it as a development dependency in your project:

Bash


npm install typescript --save-dev

2. Create a tsconfig.json File This file is the heart of your TypeScript project. It tells the compiler how to translate your .ts files into .js files. The easiest way to create one is to run:

Bash


tsc --init

This will generate a tsconfig.json file with many options, most of which are commented out.

Key tsconfig.json Options

You don't need to know all the options, but here are a few of the most important ones to get started:

  • target: Specifies the JavaScript version the compiler will output. "ES2016" is a safe default. If you need to support very old browsers, you might use "ES5". "target": "ES2016"
  • module: Defines the module system for the outputted JavaScript. "CommonJS" is standard for Node.js, while "ESNext" is used for modern browser-based code that supports ES Modules. "module": "CommonJS"
  • rootDir: The location of your TypeScript source files. "rootDir": "./src"
  • outDir: Where the compiled JavaScript files should be placed. It's best practice to keep source and output files separate. "outDir": "./dist"
  • strict: This is a very important one! Setting "strict": true enables a whole suite of strict type-checking rules. It's highly recommended to always have this on. It makes TypeScript much more effective at catching bugs.

Once you have a .ts file (e.g., index.ts) and your tsconfig.json is configured, you can compile your code by running tsc in your terminal. This will read your config file and generate the JavaScript output in your outDir.