docs: function (pointer, event, eventTarget) {
              if (this.prevTap
                  && event.clientX === this.prevTap.clientX
                  && event.clientY === this.prevTap.clientY
                  && eventTarget   === this.prevTap.target) {
  
                  this.downTargets[0] = eventTarget;
                  this.downTimes[0] = new Date().getTime();
                  this.collectEventTargets(pointer, event, eventTarget, 'tap');
              }
          }