# Mastering TypeScript TypeScript is a strongly typed programming language that builds on JavaScript, giving you better tooling at any scale. ## Why TypeScript? TypeScript adds optional type annotations to JavaScript. These annotations allow tools to catch errors early, provide better IDE support, and serve as documentation. ## Core Concepts ### Type Annotations ```typescript let greeting: string = "Hello, TypeScript!"; let count: number = 42; let isActive: boolean = true; ``` ### Interfaces ```typescript interface User { id: number; name: string; email: string; role: 'admin' | 'user' | 'guest'; } ``` ### Generics ```typescript function identity(arg: T): T { return arg; } ``` ## Advanced Patterns ### Discriminated Unions ```typescript type Result = | { success: true; data: T } | { success: false; error: string }; ``` ### Utility Types TypeScript provides built-in utility types like `Partial`, `Pick`, `Omit`, and `Record` for common type transformations. ## Best Practices 1. Enable `strict` mode in tsconfig.json 2. Use interfaces for object shapes 3. Leverage type inference when possible 4. Avoid `any` type