1、tap事件实现
zepto 源码里面看关于tap的实现方法：
$(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[0]
if (e.touches && e.touches.length === 1 && touch.x2) {
// Clear out touch movement data if we have it sticking around
// This can occur if touchcancel doesn't fire due to preventDefault, etc.
touch.x2 = undefined
touch.y2 = undefined
}
now = Date.now()
delta = now - (touch.last || now)
touch.el = $('tagName' in firstTouch.target ?
firstTouch.target : firstTouch.target.parentNode)
touchTimeout && clearTimeout(touchTimeout)
touch.x1 = firstTouch.pageX
touch.y1 = firstTouch.pageY
if (delta > 0 && delta <= 250) touch.isDoubleTap = true
touch.last = now
longTapTimeout = setTimeout(longTap, longTapDelay)
// adds the current touch contact for IE gesture recognition
if (gesture && _isPointerType) gesture.addPointer(e.pointerId);
})
.on('touchmove MSPointerMove pointermove', function(e){
if((_isPointerType = isPointerEventType(e, 'move')) &&
!isPrimaryTouch(e)) return
firstTouch = _isPointerType ? e : e.touches[0]
cancelLongTap()
touch.x2 = firstTouch.pageX
touch.y2 = firstTouch.pageY
deltaX += Math.abs(touch.x1 - touch.x2)
deltaY += Math.abs(touch.y1 - touch.y2)
})
.on('touchend MSPointerUp pointerup', function(e){
if((_isPointerType = isPointerEventType(e, 'up')) &&
!isPrimaryTouch(e)) return
cancelLongTap()
// swipe
if ((touch.x2 && Math.abs(touch.x1 - touch.x2) > 30) ||
(touch.y2 && Math.abs(touch.y1 - touch.y2) > 30))
swipeTimeout = setTimeout(function() {
touch.el.trigger('swipe')
touch.el.trigger('swipe' + (swipeDirection(touch.x1, touch.x2, touch.y1, touch.y2)))
touch = {}
}, 0)
// normal tap
else if ('last' in touch)
// don't fire tap when delta position changed by more than 30 pixels,
// for instance when moving to a point and back to origin
if (deltaX < 30 && deltaY < 30) {
// delay by one tick so we can cancel the 'tap' event if 'scroll' fires
// ('tap' fires before 'scroll')
tapTimeout = setTimeout(function() {
// trigger universal 'tap' with the option to cancelTouch()
// (cancelTouch cancels processing of single vs double taps for faster 'tap' response)
var event = $.Event('tap')
event.cancelTouch = cancelAll
touch.el.trigger(event)
// trigger double tap immediately
if (touch.isDoubleTap) {
if (touch.el) touch.el.trigger('doubleTap')
touch = {}
}
// trigger single tap after 250ms of inactivity
else {
touchTimeout = setTimeout(function(){
touchTimeout = null
if (touch.el) touch.el.trigger('singleTap')
touch = {}
}, 250)
}
}, 0)
} else {
touch = {}
}
deltaX = deltaY = 0
})
// when the browser window loses focus,
// for example when a modal dialog is shown,
// cancel all ongoing events
.on('touchcancel MSPointerCancel pointercancel', cancelAll)
// scrolling the window indicates intention of the user
// to scroll, not tap or swipe, so cancel all ongoing events
$(window).on('scroll', cancelAll)
})
;['swipe', 'swipeLeft', 'swipeRight', 'swipeUp', 'swipeDown',
'doubleTap', 'tap', 'singleTap', 'longTap'].forEach(function(eventName){
$.fn[eventName] = function(callback){ return this.on(eventName, callback) }
})
zepto的tap通过兼听绑定在document上的touch事件来完成tap事件的模拟的,及tap事件是冒泡到document上触发的再点击完成时的tap事件(touchstart\touchend)需要冒泡到document上才会触发，而在冒泡到document之前，用户手的接触屏幕(touchstart)和离开屏幕(touchend)是会触发click事件的,因为click事件有延迟触发(这就是为什么移动端不用click而用tap的原因)(大概是300ms,为了实现safari的双击事件的设计)，所以在执行完tap事件之后，弹出来的选择组件马上就隐藏了，此时click事件还在延迟的300ms之中，当300ms到来的时候，click到的其实不是完成而是隐藏之后的下方的元素，如果正下方的元素绑定的有click事件此时便会触发，如果没有绑定click事件的话就当没click，但是正下方的是input输入框(或者select选择框或者单选复选框)，点击默认聚焦而弹出输入键盘，这就是常出现的“点透”的情况。
下面一个例子看看点透是什么情况：
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title></title>
<style type="text/css">
input {
width: 200px;
height: 50px;
}
.layer {
width: 200px;
height: 200px;
position: absolute;
left: 0;
top: 0;
background: red;
opacity: .5;
}
</style>
</head>
<body>
<div class="layer" id="J_layer"></div>
<input type="text"> <script type="text/javascript" src="/lib/zepto.js"></script>
<script type="text/javascript">
$('#J_layer').on('tap', function () {
var $this = $(this);
$this.hide();
});
</script>
</body>
</html>
运行出来的情况是：
当点击“layer”处于“input”上方区域后出现：
上图可以看出，input获取到了焦点。
这就是点透现象，input获取到了click事件。
2、解决“点透”问题
2.1、引入fastclick.js，因为fastclick源码不依赖其他库所以你可以在原生的js前直接加上。https://github.com/ftlabs/fastclick
window.addEventListener( "load", function() {
FastClick.attach( document.body );
}, false );
2.2、用touchend代替tap事件并阻止掉touchend的默认行为preventDefault()
$("#layer").on("touchend", function (event) {
//很多处理比如隐藏什么的
event.preventDefault();
});
2.3、延迟一定的时间(300ms+)来处理事件
$("#layer").on("tap", function (event) {
setTimeout(function(){
//程序处理
},320);
});
以上就是对zepto中tap方法的解说，请大家多多提问