TypeScript

TypeScript is a typed superset of JavaScript that compiles to plain JavaScript. Developed by Microsoft, it adds static type checking to JavaScript, catching errors at compile time rather than runtime.

Key Features

• Static typing: Catch type errors before running code
• Type inference: Types often inferred automatically
• IDE support: Exceptional autocomplete and refactoring
• JavaScript compatibility: All valid JS is valid TS
• Gradual adoption: Add types incrementally

Type System Basics

// Basic types
const name: string = 'Alice';
const age: number = 30;
const active: boolean = true;

// Arrays and objects
const items: string[] = ['a', 'b', 'c'];
const user: { name: string; age: number } = { name: 'Bob', age: 25 };

// Interfaces
interface User {
  id: number;
  name: string;
  email: string;
  role?: 'admin' | 'user'; // Optional union type
}

// Generics
function first<T>(items: T[]): T | undefined {
  return items[0];
}

// Utility types
type PartialUser = Partial<User>;
type ReadonlyUser = Readonly<User>;
type UserKeys = keyof User;

TypeScript vs JavaScript

Aspect	TypeScript	JavaScript
Type safety	Compile-time	Runtime only
IDE support	Excellent	Good
Learning curve	Higher	Lower
Build step	Required	Optional
Refactoring	Safe	Risky

What We Like

• Error prevention: Catches bugs before they reach production
• Documentation: Types serve as inline documentation
• Refactoring: Safe, confident code changes
• IDE experience: Autocomplete, go-to-definition, rename
• Ecosystem: First-class support in modern frameworks

What We Don't Like

• Build complexity: Additional compilation step
• Type gymnastics: Complex types can be hard to understand
• Learning curve: Advanced features require study
• Third-party types: Some libraries have incomplete or incorrect types
• Configuration: tsconfig.json options can be overwhelming

Best Practices

1. Enable strict mode: Get the full benefit of type checking
2. Prefer interfaces: For object shapes (extend better than type intersections)
3. Avoid any: Use unknown if type is truly unknown
4. Use type inference: Don't over-annotate obvious types
5. Learn utility types: Partial, Required, Pick, Omit, etc.

When to Use TypeScript

We recommend TypeScript for:

• Any project beyond trivial scripts
• Team projects where code is shared
• Long-term codebases requiring maintenance
• Projects using React, Vue, or Angular

The initial investment pays off quickly in reduced bugs and improved developer experience.