code: function () {
      var sceneEl = this.el.sceneEl;
      var canvasEl = sceneEl.canvas;
  
      // Wait for canvas to load.
      if (!canvasEl) {
        sceneEl.addEventListener('render-target-loaded', bind(this.addEventListeners, this));
        return;
      }
  
      // Mouse events.
      canvasEl.addEventListener('mousedown', this.onMouseDown, false);
      window.addEventListener('mousemove', this.onMouseMove, false);
      window.addEventListener('mouseup', this.onMouseUp, false);
  
      // Touch events.
      canvasEl.addEventListener('touchstart', this.onTouchStart);
      window.addEventListener('touchmove', this.onTouchMove);
      window.addEventListener('touchend', this.onTouchEnd);
  
      // sceneEl events.
      sceneEl.addEventListener('enter-vr', this.onEnterVR);
      sceneEl.addEventListener('exit-vr', this.onExitVR);
  
      // Pointer Lock events.
      if (this.data.pointerLockEnabled) {
        document.addEventListener('pointerlockchange', this.onPointerLockChange, false);
        document.addEventListener('mozpointerlockchange', this.onPointerLockChange, false);
        document.addEventListener('pointerlockerror', this.onPointerLockError, false);
      }
    }
docs: Add mouse and touch event listeners to canvas.