code: function () {
      var changed = false;
      var controllerAxes = this.controller.axes;
      var i;
      var previousAxis = this.axis;
      var changedAxes = this.changedAxes;
  
      // Check if axis changed.
      this.changedAxes.length = 0;
      for (i = 0; i < controllerAxes.length; ++i) {
        changedAxes.push(previousAxis[i] !== controllerAxes[i]);
        if (changedAxes[i]) { changed = true; }
      }
      if (!changed) { return false; }
  
      this.axis.length = 0;
      for (i = 0; i < controllerAxes.length; i++) {
        this.axis.push(controllerAxes[i]);
      }
      this.el.emit(EVENTS.AXISMOVE, this.axisMoveEventDetail, false);
      return true;
    }
docs: An axis is an array of values from -1 (up, left) to 1 (down, right).
  Compare each component of the axis to the previous value to determine change.
  
  @returns {boolean} Whether axes changed.