TypeScript - Generic Functions and Generic Classes

Last Updated : 23 Jul, 2025

Generics in TypeScript enable functions and classes to work with multiple data types while ensuring type safety. Generic functions provide reusable logic that adapts to various inputs, while generic classes help define flexible and type-safe structures.

Generic Functions

A generic function allows you to define a function that works with multiple data types without losing the type safety that TypeScript provides. It enables you to use different types while maintaining the correct type throughout the function's operations.

JavaScript

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

console.log(id(5));
console.log(id("Hello"));

Output

5
Hello

In this example

The identity function accepts a value of any type and returns it unchanged.
The type T is inferred based on the argument passed, so it works for both number and string without any additional changes.

Usage of Generic Functions

Type Safety: Provides the benefit of type safety, ensuring that the input and output types are consistent.
Code Reusability: Reuse the same function with different types without rewriting or overloading.
Maintainability: Reduces the number of functions you need to maintain, as a generic function can handle various types.

For more details read the article - TypeScript Generic Functions

Generic Classes

Generic classes allow you to define a class that can handle multiple types of data while ensuring type safety. By using generics in classes, you can create data structures or components that work with different types of data.

JavaScript

class Box<T> {
    private value: T;

    constructor(value: T) {
        this.value = value;
    }

    getValue(): T {
        return this.value;
    }

    setValue(value: T): void {
        this.value = value;
    }
}
const numBox = new Box<number>(123);
console.log(numBox.getValue());  

const strBox = new Box<string>("Hello");
console.log(strBox.getValue());

Output

123
Hello

In this example

The Box class is defined with a generic type T. This means it can hold any type of value, but the type is determined when an instance of Box is created.
In the example, we create two instances: one with a number and another with a string. The Box class enforces type safety, ensuring that only the specified type can be used.

Usage of Generic Classes

Reusability: A single generic class can work with multiple types without being rewritten.
Type Safety: Like generic functions, generic classes ensure type safety by enforcing that the properties and methods of the class are consistent with the provided type.
Flexibility: They provide flexibility in handling various types of data, making your code more general and adaptable

For more details read the article - TypeScript Generic Classes

TypeScript Generic Parameter Defaults

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TypeScript - Generic Functions and Generic Classes

Generic Functions

Usage of Generic Functions

Generic Classes

Usage of Generic Classes

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