What is the difference between type and class in Typescript?

Question

What is the difference between type and class?

type Point {
  x: number, y: number
}

let p = new Point();

The ab

Answer 1

You use a type (or in other cases an interface) for type annotations to indicate the structure of JavaScript objects:

type Point = {
  x: number, y: number
}

function doSomething(p: Point) {
}

let p: Point = { x: 10, y: 15 };
doSomething(p);

These type annotations are subject to structural typing, meaning that in this specific case you could drop the type annotation:

let p = { x: number, y: number };
doSomething(p);

A class is something entirely different, which provides you a more elegant alternative to JS prototype inheritance:

class Point {
    public x: number;
    public y: number;

    constructor(x: number, y: number) {
        this.x = x;
        this.y = y;
    }

    public move(deltaX: number, deltaY: number) {
        this.x = this.x + deltaX;
        this.y = this.y + deltaY;
    }
}

let p = new Point(10, 15);
p.move(1, 2);

When you look at the generated JS code, you will quickly notice the difference:

The type declaration is dropped in the generated code.

The class definition is turned into a JS function with prototype inheritance