TypeScript from Scratch

What is TypeScript?

TypeScript is a superset of JavaScript that adds static typing and other advanced features to JavaScript.

How does TypeScript work?

TypeScript code is written in files with the .ts extension. Before you can run it, it is compiled to JavaScript.

Installing TypeScript

To use TypeScript, you need to install it with NPM (Node Package Manager).

You will also need a development IDE, such as Visual Studio Code.

Types in TypeScript

TypeScript allows you to use basic types for variables and functions, such as string, number, boolean, and more.

For example:

let name: string = "Luis";
let age: number = 25;

But you can also create custom types, for example using type.

Arrays and Tuples

We can also define arrays and tuples:

• Array: Declared with type[] or Array<type>.
• Tuple: Defines a collection of fixed length and specific types.

let numbers: number[] = [1, 2, 3]; // array
let pair: [string, number] = ["age", 30];  // Tuple

Union Types and Literal Types

Literal and union types use the | operator to combine values or types.

• Literal: Specifies allowed fixed values.
• Union: Allows a variable to accept multiple types.

let direction: "north" | "south" | "east" | "west"; // literal

let result: number | string = 42; // union

Classes and Interfaces

TypeScript also adds many features of object-oriented programming.

For example, you can define classes, with methods, attributes, encapsulation, and inheritance.

You can also use interfaces that specify what properties and methods must be present.

Getting Started with TypeScript

Create a file with the .ts extension, like app.ts. Inside it, write this code:

let message: string = "Hello, LuisLlamas.es!";
console.log(message);

Write TypeScript code in this file, and then compile it to JavaScript using the command tsc app.ts.

Compiling TypeScript

Use the tsc command to compile TypeScript files to JavaScript.

This will generate a hello.js file with the same code in JavaScript.

Running the Code

Finally, run the compiled file using Node.js:

node hello.js

Congratulations! You just created your first program in TypeScript. Ready to keep progressing!