Input class to capture keyboard and mouse events.

Input.js

class Input {
  constructor(el = document) {
    this.keys = [];
    this.mouse = [];
    this.mousemoveHandlers = [];
    this.mousedownHandlers = [];
    this.mouseupHandlers = [];

    document.addEventListener("keydown", e => {
      this.keys[e.key] = true;
    });

    document.addEventListener("keyup", e => {
      this.keys[e.key] = false;
    });

    el.addEventListener("mousedown", e => {
      e.preventDefault();
      this.mouse[e.which] = true;
      this.mousedownHandlers.forEach(h => h(e))
    });

    el.addEventListener("mouseup", e => {
      this.mouse[e.which] = false;
      this.mouseupHandlers.forEach(h => h(e))
    });

    el.addEventListener("mouseleave", e => {
      this.mouse = [];
    });

    el.addEventListener("mousemove", e => {
      this.mousemoveHandlers.forEach(h => h(e))
    });
  }
}