Mastering TypeScript: Building Type-Safe Applications

Introduction to TypeScript

TypeScript is a strongly typed programming language that builds on JavaScript, giving you better tooling at any scale. It adds optional static types, classes, and modules to JavaScript, making it easier to develop robust applications.

Key Features

1. Type System

// Basic Types
let isDone: boolean = false;
let decimal: number = 6;
let color: string = "blue";
let list: number[] = [1, 2, 3];

2. Interfaces

interface User {
  name: string;
  id: number;
  email?: string; // Optional property
}

const user: User = {
  name: "John",
  id: 1,
};

3. Generics

function getArray<T>(items : T[] ) : T[] {
    return new Array<T>().concat(items);
}

Best Practices

1. Use Type Inference

   • Let TypeScript infer types when possible
   • Explicit types when inference isn't clear

2. Strict Mode

   • Enable strict mode in tsconfig.json
   • Catches more potential errors

3. Union Types

   type Status = "pending" | "approved" | "rejected";
   

Advanced Concepts

Utility Types

type Partial<T> = {
    [P in keyof T]?: T[P];
};

type ReadOnly<T> = {
    readonly [P in keyof T]: T[P];
};

Decorators

function logged(target: any) {
    console.log(`New instance created of ${target.name}`);
}

@logged
class Example {
    constructor() {
        console.log('Instance created');
    }
}

Conclusion

TypeScript provides powerful tools for building scalable JavaScript applications. Its type system helps catch errors early in development and improves code maintainability.

Resources

• Official TypeScript Documentation
• TypeScript GitHub Repository
• TypeScript Playground