Generics Basics

Generics let you write code that works with many types safely.

Simple generic function

function identity<T>(value: T): T {
  return value;
}

identity<number>(10);
identity<string>("hello");

Generic array function

function first<T>(arr: T[]): T {
  return arr[0];
}

first([1, 2, 3]);
first(["a", "b"]);

Generic interface

interface ApiResponse<T> {
  data: T;
  status: number;
}

const res: ApiResponse<string> = {
  data: "ok",
  status: 200,
};

Graph: generics idea

flowchart LR
  A[Generic T] --> B[Used with number]
  A --> C[Used with string]
  A --> D[Used with objects]

Remember

• generics = reusable + safe
• avoid repeating same logic for many types