1. What are interfaces

How can you assign types to objects? For example, a user object that looks like this -

const user = {
	firstName: "harkirat",
	lastName: "singh",
	email: "email@gmail.com".
	age: 21,
}

To assign a type to the user object, you can use interfaces

interface User {
	firstName: string;
	lastName: string;
	email: string;
	age: number;
}

Assignment #1 - Create a function isLegal that returns true or false if a user is above 18. It takes a user as an input.

• Solution

Assignment #2 - Create a React component that takes todos as an input and renders them

💡Select typescript when initialising the react project using npm create vite@latest

• Solution

2. Implementing interfaces

Interfaces have another special property. You can implement interfaces as a class.

Let’s say you have an personinterface -

interface Person {
    name: string;
    age: number;
    greet(phrase: string): void;
}

You can create a class which implements this interface.

class Employee implements Person {
    name: string;
    age: number;

    constructor(n: string, a: number) {
        this.name = n;
        this.age = a;
    }

    greet(phrase: string) {
        console.log(`${phrase} ${this.name}`);
    }
}

This is useful since now you can create multiple variants of a person (Manager, CEO …)

Summary

1. You can use interfaces to aggregate data