Typescript

Node doesn’t run typescript file. It runs the Javascript file that is compiled from typescript.

Structural Type System

Type checking focuses on the shape that values have. This is called Structural Typing or Duck Typing.

interface Point{
	x: number;
	y: number;
}
 
function logPoint(p: Point) {
	console.log(`${p.x}, ${p.y}`)
}
 
// Never defined as Point type. But still checks out
const point = { x: 10 , y: 20};
logPoint(point);

And this is also true if the subsets of the object’s fields match.

const point2 = { x: 10 , y: 20, z: 30};
logPoint(point2);

And a Class is no different from an object in this case:

class VirtualPoint{
	x: number;
	y: number;
 
	constructor(x: number, y: number){
		this.x = x;
		this.y = y;
	}
}
 
const newPoint = new VirtualPoint(10, 20);
logPoint(newPoint);

Typescript Uses