Classes and modules in #TypeScript.

main.ts

// import syntax is kinda just opposite from Python
import {Point} from './point';

let point = new Point();
let x = point.X;
point.X = 10;
point.draw();

point.ts

// exporting exposes the class to other files
export class Point {
    // access modifier private, public are by default
    private x: number;
    private y: number;

    // constructor is like __init__ in Python
    // with ?, it's an optional argument
    // but with ?, all the param right to that should also be optional
    constructor(x?: number, y?: number) {
        this.x = x;
        this.y = y;
    }

    // alternative constructor, which allows to remove line 3-4 on top
    // constructor(private x?: number, private y?: number) {
    // }

    // these are the methods; this is analogous to self in python
    draw() {
        console.log("X: " + this.x + ", Y: " + this.y);
    }

    // getters and setter are somewhat different in typescript
    // get and set are reserved keywords
    // you don't need paren to get or set values
    get X() {
        return this.x;
    }

    set X(value) {
        if (value < 0) {
            throw new Error("Value cannot be less than zero.");
        }
        this.x = value;
    }
}