TypeScript Programming Language Cheatsheet

TypeScript has gained immense popularity in the world of web development due to its ability to add static typing to JavaScript. Developed and maintained by Microsoft, TypeScript extends JavaScript by introducing optional static types, which can catch common errors and improve code maintainability. If you’re new to TypeScript or looking for a quick reference guide, this cheatsheet is designed to help you get started and navigate the language efficiently.

Basics

1. Variable Declaration

let variableName: type = value;

2. Type Annotations

let variableName: number = 10;
let stringVariable: string = "Hello, TypeScript!";
let booleanVariable: boolean = true;

3. Functions

function add(a: number, b: number): number {
    return a + b;
}

4. Arrays

let numbers: number[] = [1, 2, 3];
let strings: Array<string> = ["one", "two", "three"];

5. Interfaces

interface Person {
    name: string;
    age: number;
}

let user: Person = {
    name: "John Doe",
    age: 30
};

Advanced Types

1. Union Types

let result: number | string;
result = 10;
result = "Hello";

2. Intersection Types

type Car = {
    brand: string;
};

type ElectricCar = {
    batteryLife: number;
};

let hybridCar: Car & ElectricCar = {
    brand: "Tesla",
    batteryLife: 300
};

3. Type Aliases

type Point = {
    x: number;
    y: number;
};

let coordinate: Point = { x: 10, y: 20 };

4. Enums

enum Color {
    Red,
    Green,
    Blue
}

let selectedColor: Color = Color.Green;

Advanced Concepts

1. Generics

function identity<T>(arg: T): T {
    return arg;
}

let output = identity<string>("Hello, Generics!");

2. Decorators

function log(target: any, key: string) {
    console.log(`${key} was called`);
}

class Example {
    @log
    someMethod() {
        // Method logic here
    }
}

3. Modules

// math.ts
export function add(a: number, b: number): number {
    return a + b;
}

// main.ts
import { add } from "./math";
let result = add(10, 20);

Type Assertion

let someValue: any = "Hello, TypeScript!";
let strLength: number = (someValue as string).length;

Conclusion

This TypeScript cheatsheet provides a quick reference for essential syntax and concepts. Whether you’re a beginner or an experienced developer, having this cheatsheet handy can help you write TypeScript code more effectively. Keep exploring the TypeScript documentation for more in-depth information and examples as you continue to enhance your web development skills. Happy coding!

For more details, always refer to the official TypeScript documentation.