/*** 跨平臺的事件監(jiān)聽函數(shù)* @param {Node} node 需要監(jiān)聽事件的DOM節(jié)點(diǎn)* @param {String} eventType 需要監(jiān)聽的事件類型* @param {Function} callback 事件監(jiān)聽回調(diào)函數(shù)* @type Function 返回值為函數(shù)類型* @return 返回監(jiān)聽回調(diào)函數(shù)的引用，用于釋放監(jiān)聽*/function bindEvent(node, eventType, callback) { if (node.attachEvent) {  if (eventType.indexOf('on')) { eventType = 'on' + eventType;}  node.attachEvent(eventType, callback); } else {  if (!eventType.indexOf('on'))   eventType = eventType.substring(2, eventType.length);  node.addEventListener(eventType, callback, false); } return callback;}/*** 跨平臺的事件監(jiān)聽卸載函數(shù)* @param {Node} node 需要卸載監(jiān)聽事件的DOM節(jié)點(diǎn)* @param {String} eventType 需要卸載監(jiān)聽的事件類型* @param {Function} callback 卸載事件監(jiān)聽回調(diào)函數(shù)*/function removeEvent(node, eventType, callback) { if (node.detachEvent) {  if (eventType.indexOf('on')) { eventType = 'on' + eventType;}  node.detachEvent(eventType, callback); } else {  if (!eventType.indexOf('on'))   eventType = eventType.substring(2, eventType.length);  node.removeEventListener(eventType, callback, false); }}/*** 兼容不同定位方式的通用拖動接口* @param {Node} dragger 需要被拖動的元素*///必須告訴系統(tǒng)，哪些元素是可以進(jìn)行交互，而哪些是不行function canDrag(dragger) { var drag = bindEvent(dragger,'onmousedown',function(e){  //兼容事件對象  e = e || event;  //兼容坐標(biāo)屬性  var pageX = e.clientX || e.pageX;  var pageY = e.clientY || e.pageY;  //兼容樣式對象  var style = dragger.currentStyle || window.getComputedStyle(dragger,null);  //當(dāng)沒有設(shè)置left和top屬性時，IE下默認(rèn)值為auto  var offX = parseInt(style.left) || 0;  var offY = parseInt(style.top) || 0;  //獲取鼠標(biāo)相對于元素的間距  var offXL = pageX - offX;  var offYL = pageY - offY;  //為dragger增加onDrag屬性，用來存儲拖動事件  if (!dragger.onDrag) {   //監(jiān)聽拖動事件   dragger.onDrag = bindEvent(document,'onmousemove',function(e){    e = e || event;    var x = e.clientX || e.pageX;    var y = e.clientY || e.pageY    //設(shè)置X坐標(biāo)    dragger.style.left = x - offXL + 'px';    //設(shè)置Y坐標(biāo)    dragger.style.top = y - offYL + 'px';   });   //監(jiān)聽拖動結(jié)束事件   dragger.onDragEnd = bindEvent(document,'onmouseup',function(e){    //釋放前讀取事件對象    var x = e.clientX || e.pageX;    var y = e.clientY || e.pageY    //釋放拖動監(jiān)聽和結(jié)束監(jiān)聽    removeEvent(document, 'onmousemove', dragger.onDrag);    removeEvent(document, 'onmouseup', dragger.onDragEnd);    try {     //刪除拖動時所用的屬性，兼容FF使用     delete dragger.onDrag;     delete dragger.onDragEnd;    } catch (e) {     //刪除拖動時所用的屬性，兼容IE6使用     dragger.removeAttribute('onDrag');     dragger.removeAttribute('onDragEnd');    }   });  } }); return function() {  //返回一個可以取消拖動功能的函數(shù)引用  //釋放拖動監(jiān)聽和結(jié)束監(jiān)聽  removeEvent(document, 'onmousemove', dragger.onDrag);  removeEvent(document, 'onmouseup', dragger.onDragEnd);  try {   //刪除拖動時所用的屬性，兼容FF使用   delete dragger.onDrag;   delete dragger.onDragEnd;  } catch (e) {   //刪除拖動時所用的屬性，兼容IE6使用   dragger.removeAttribute('onDrag');   dragger.removeAttribute('onDragEnd');  } }}