What are generics in TypeScript and why would you use them? Provide an example.

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## What are Generics? **Generics** in TypeScript allow you to create reusable components that work with a variety of types while maintaining type safety. Instead of using `any` (which loses type information), generics preserve the relationship between input and output types. ## Basic Syntax ```typescript // Generic function function identity(value: T): T { return value; } // Usage - TypeScript infers the type const num = identity(42); // type: number const str = identity("hello"); // type: string ``` ## Why Use Generics? ### 1. Type Safety with Flexibility Without generics: ```typescript function getFirst(arr: any[]): any { return arr[0]; } const first = getFirst([1, 2, 3]); // type: any - we lost the number type! ``` With generics: ```typescript function getFirst(arr: T[]): T { return arr[0]; } const first = getFirst([1, 2, 3]); // type: number - preserved! ``` ### 2. Reusable Data Structures ```typescript interface ApiResponse { data: T; status: number; message: string; } // Can be used with any data type const userResponse: ApiResponse = { ... }; const productResponse: ApiResponse = { ... }; ``` ### 3. Generic Classes ```typescript class Stack { private items: T[] = []; push(item: T): void { this.items.push(item); } pop(): T | undefined { return this.items.pop(); } } const numberStack = new Stack(); numberStack.push(1); numberStack.push("two"); // Error! Can only push numbers ``` ## Generic Constraints You can constrain what types are allowed: ```typescript interface HasLength { length: number; } function logLength(item: T): void { console.log(item.length); } logLength("hello"); // OK - string has length logLength([1, 2, 3]); // OK - array has length logLength(123); // Error - number doesn't have length ``` Generics are essential for building type-safe APIs, utility functions, and reusable components.