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TypeScript: Generics

1. What are Generics?​

Generics are used to create highly reusable components. They allow you to define functions or classes that can work with a variety of types rather than being restricted to a single one.

2. Generic Functions​

A type parameter <T> is used to determine the type at the time of the function call.

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

let output1 = identity<string>("myString");
let output2 = identity<number>(100);

3. Generic Interfaces​

Generics can also be applied to interfaces to make them more flexible.

interface Box<T> {
  content: T;
}

const stringBox: Box<string> = { content: "Apple" };
const numberBox: Box<number> = { content: 123 };

4. Generic Constraints​

Using the extends keyword, you can restrict the types that can be used with a generic to those that meet specific criteria.

interface Lengthwise {
  length: number;
}

function loggingIdentity<T extends Lengthwise>(arg: T): T {
  console.log(arg.length); // Guaranteed to have a length property
  return arg;
}

loggingIdentity({ length: 10, value: 3 });
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