typescript readonly

by Alejandro M

HTML

readonly vs const

The easiest way to remember whether to use readonly or const is to ask whether you’re using it on a variable or a property. Variables use const whereas properties use readonly.

TypeScript

interface Point {
    readonly x: number;
    readonly y: number;
}
let p1: Point = { x: 10, y: 20 };
alert(p1);
p1.x = 5; // error!