Zepto.js touch模块深入分析

目的：记录 Zepto.js touch模块 源码阅读

源码：

//     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[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)

分析：

var now, delta, touch = {};$(document)    .on('touchstart', startListener)    .on('touchmove', moveListener)    .on('touchend', endListener);

1、是单击还是双击

function startListener(e){    now = Date.now();    delta = now - (touch.last || now);    // 手指连续轻触两次，时间间隔大于0，小于等于.25s，则为双击，反之单击    if ( delta > 0 && delta <= 250 ) {        touch.isDoubleTap = true;    }    touch.last = now;}

2、处理手指长按

var longTapTimeout, longTapDelay = 750;function longTap() {    longTapTimeout = null    if (touch.last) {        touch.el.trigger('longTap')