What are generics in TypeScript and why do you need them

The problem generics solve

Without generics, a function that works with multiple types must use any, losing all type safety:

function identity(value: any): any { return value; }
const result = identity("hello"); // result is any, not string

With generics, the type is captured and returned:

function identity(value: T): T { return value; }
const result = identity("hello"); // result is string
const num    = identity(42);      // num is number

Type parameter inference

The compiler infers T from the argument, so you can usually leave it unspecified:

identity("hello"); // explicit
identity("hello");         // inferred - preferred

Naming conventions

Single letters are conventional: T for a general type, K for key, V for value, E for element. For clarity in complex generics, use descriptive names like TItem or TPayload.

Think of T as a variable for a type. The function does not care what type it holds - it guarantees only that input and output types match.