让 jQuery UI draggable 适配移动端

背景：

在移动端，本人要实现对某个元素的拖动，想到使用 jQuery UI 的 draggable 功能。但是发现此插件的拖动只支持PC端，不支持移动端。

原因：

原始的 jQuery UI 里，都是mousedown、mousemove、mouseup来描述拖拽和鼠标的点击事件，而在移动端里，肯定要新添touchstart、touchmove、touchend来描述拖拽和手指的点击事件

实现 demo：

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0;" name="viewport"><title>jQuery UI draggable 适配移动端</title>
</head>
<body>
<img id="img" src="http://placehold.it/200x100"><script src="//cdn.bootcss.com/jquery/3.0.0-beta1/jquery.js"></script>
<script src="//cdn.bootcss.com/jqueryui/1.11.4/jquery-ui.min.js"></script>
<script>// jQuery UI draggable 适配移动端var moveFlag = 0; // 是否移动的flag// /iPad|iPhone|Android/.test( navigator.userAgent ) &&
    (function ($) {var proto = $.ui.mouse.prototype, _mouseInit = proto._mouseInit;$.extend(proto, {_mouseInit: function () {this.element.bind("touchstart." + this.widgetName, $.proxy(this, "_touchStart"));_mouseInit.apply(this, arguments);}, _touchStart: function (event) {this.element.bind("touchmove." + this.widgetName, $.proxy(this, "_touchMove")).bind("touchend." + this.widgetName, $.proxy(this, "_touchEnd"));this._modifyEvent(event);$(document).trigger($.Event("mouseup"));//reset mouseHandled flag in ui.mousethis._mouseDown(event);//console.log(this);//return false;//--------------------touchStart do something--------------------
                console.log("i touchStart!");}, _touchMove: function (event) {moveFlag = 1;this._modifyEvent(event);this._mouseMove(event);//--------------------touchMove do something--------------------
                console.log("i touchMove!");}, _touchEnd: function (event) {// 主动触发点击事件if (moveFlag == 0) {var evt = document.createEvent('Event');evt.initEvent('click', true, true);this.handleElement[0].dispatchEvent(evt);}this.element.unbind("touchmove." + this.widgetName).unbind("touchend." + this.widgetName);this._mouseUp(event);moveFlag = 0;//--------------------touchEnd do something--------------------
                console.log("i touchEnd!");}, _modifyEvent: function (event) {event.which = 1;var target = event.originalEvent.targetTouches[0];event.pageX = target.clientX;event.pageY = target.clientY;}});})(jQuery);</script>
<script>// my js
    $("#img").draggable();
</script>
</body>
</html>