A mutable 2D vector class, made for real-time graphics in JS

vec2d.js

class Vec2d {
  constructor(x, y) { this.reset(x, y); }
  get mag() { return Math.sqrt(this.dot(this)); }
  clone() { return new Vec2d(this.x, this.y); }
  reset(x, y) { this.x = x; this.y = y; return this; }
  neg() { return this.scale(-1); }
  norm() {
    let m = this.mag;
    if (m > 0) return this.scale(1 / m);
    return this;
  }
  add(a, b) {
    let x, y;
    if (a instanceof Vec2d) {
      x = a.x; y = a.y;
    } else {
      x = a; y = b;
    }
    this.x += x;
    this.y += y;
    return this;
  }
  sub(a, b) {
    let x, y;
    if (a instanceof Vec2d) {
      x = a.x; y = a.y;
    } else {
      x = a; y = b;
    }
    this.x -= x;
    this.y -= y;
    return this;
  }
  scale(a) {
    this.x *= a;
    this.y *= a;
    return this;
  }
  dot(a, b) {
    let x, y;
    if (a instanceof Vec2d) {
      x = a.x; y = a.y;
    } else {
      x = a; y = b;
    }
    return this.x * x + this.y * y;
  }
  static add(a, b) { return a.clone().add(b); }
  static sub(a, b) { return a.clone().sub(b); }
  static dot(a, b) { return a.dot(b); }
}