Zepto.js touch模块深入分析

//	 Zepto.js
//	 (c) 2010-2015 Thomas Fuchs
//	 Zepto.js may be freely distributed under the MIT license.

;
(function($) {
  var touch = {},
    touchTimeout, tapTimeout, swipeTimeout, longTapTimeout,
    longTapDelay = 750,
    gesture
    function swipeDirection(x1, x2, y1, y2) {
      return Math.abs(x1 - x2) >=
        Math.abs(y1 - y2) ? (x1 - x2 > 0 ? 'Left' : 'Right') : (y1 - y2 > 0 ? 'Up' : 'Down')
    }
    function longTap() {
      longTapTimeout = null
      if (touch.last) {
        touch.el.trigger('longTap')
        touch = {}
      }
    }
    function cancelLongTap() {
      if (longTapTimeout) clearTimeout(longTapTimeout)
      longTapTimeout = null
    }
    function cancelAll() {
      if (touchTimeout) clearTimeout(touchTimeout)
      if (tapTimeout) clearTimeout(tapTimeout)
      if (swipeTimeout) clearTimeout(swipeTimeout)
      if (longTapTimeout) clearTimeout(longTapTimeout)
      touchTimeout = tapTimeout = swipeTimeout = longTapTimeout = null
      touch = {}
    }
    function isPrimaryTouch(event) {
      return (event.pointerType == 'touch' ||
        event.pointerType == event.MSPOINTER_TYPE_TOUCH) && event.isPrimary
    }
    function isPointerEventType(e, type) {
      return (e.type == 'pointer' + type ||
        e.type.toLowerCase() == 'mspointer' + type)
    }
  $(document).ready(function() {
    var now, delta, deltaX = 0,
      deltaY = 0,
      firstTouch, _isPointerType
    if ('MSGesture' in window) {
      gesture = new MSGesture()
      gesture.target = document.body
    }
    $(document)
      .bind('MSGestureEnd', function(e) {
        var swipeDirectionFromVelocity =
          e.velocityX > 1 ? 'Right' : e.velocityX < -1 ? 'Left' : e.velocityY > 1 ? 'Down' : e.velocityY < -1 ? 'Up' : null;
        if (swipeDirectionFromVelocity) {
          touch.el.trigger('swipe')
          touch.el.trigger('swipe' + swipeDirectionFromVelocity)
        }
      })
      .on('touchstart MSPointerDown pointerdown', function(e) {
        if ((_isPointerType = isPointerEventType(e, 'down')) && !isPrimaryTouch(e)) return
        firstTouch = _isPointerType ? e : e.touches[