https://eloquentjavascript.net/06_object.html#i_zO8FRQBMAy

Eloquent JavaScript 0601 A Vector Type.js

// Your code here.
class Vec {
  constructor(x, y) {
    this.x = x;
    this.y = y;
  }
 
  plus(parameter) {
    return new Vec(this.x + parameter.x, this.y + parameter.y);
  }
  
  minus(parameter) {
    return new Vec(this.x - parameter.x, this.y - parameter.y);
  }
  
  get length() {
    return Math.sqrt(this.x * this.x + this.y * this.y);
  }
}

console.log(new Vec(1, 2).plus(new Vec(2, 3)));
// → Vec{x: 3, y: 5}
console.log(new Vec(1, 2).minus(new Vec(2, 3)));
// → Vec{x: -1, y: -1}
console.log(new Vec(3, 4).length);
// → 5