本文實例為大家分享的是一個拖放的效果，參考的代碼，重構以下，加以理解學習。
首先來看效果：
拖動div
拖放狀態：未開始
【程序說明】
拖動原理：其實就是在拖動塊上監聽mousedown事件，鼠標點擊時，通過事件對象獲取對應的坐標參數。然后鼠標移動時再監聽document上的mousemove事件，獲取鼠標的clientX 和clientY坐標然后設置拖動塊的left 和 top。
首先是監聽mousedown事件
//監聽mousemove 和 mouseup事件EventUtil.addEventHandler(document, "mousemove", this._fM);EventUtil.addEventHandler(document, "mouseup", this._fS);
鼠標移動時，設置拖動塊的left 和 top 屬性 ：
if(!this.LockX)this.Drag.style.left = iLeft + "px"; if(!this.LockY)this.Drag.style.top = iTop + "px";
水平和垂直鎖定：通過判斷LockX 和lockY屬性來限制對于的top 和 left 屬性即可。
范圍限制鎖定：通過計算容器的寬高和拖動塊的寬高差值來設定最大left值和top值，來限制拖動塊的left值和top值會在一定的范圍里。
完整DEMO：
<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <title>JavaScript拖放效果</title> <style type="text/css"> </style></head><body> <div id="drag-wrap" style="height: 300px;margin:10px;border:5px solid #FF8000;background:#8080C0;position: relative;"> <div class="draggable" id="drag" style="width:100px;height: 100px;position: absolute;top: 100px;left:100px;background:#eee;border:1px solid #aceaac;cursor: move;">拖動div</div> </div> <input id="idReset" type="button" value="復位" /> <input id="idLock" type="button" value="鎖定全部" /> <input id="idLockX" type="button" value="鎖定水平" /> <input id="idLockY" type="button" value="鎖定垂直" /> <input id="idLimit" type="button" value="范圍鎖定" /> <input id="idLimitOff" type="button" value="取消范圍鎖定" /> <br />拖放狀態：<span id="idShow">未開始</span> <script type="text/javascript"> /** *工具函數 */ var isIE = (document.all) ? true : false ; var $$ = function(id){ return "string" == typeof id ? document.getElementById(id) : id; }; var Class = { create: function() { return function() { this.initialize.apply(this, arguments); } } }; var Extend = function(destination,source){ for(var property in source){ destination[property] = source[property]; } }; var BindAsEventListener = function(object,func){ return function(event){ return func.call(object,event || window.event); } }; var Bind = function(object,func){ return function(){ return func.apply(object,arguments); } }; /** *跨瀏覽器事件對象 */ var EventUtil = { //事件注冊處理程序 addEventHandler:function(oTarget,sEventType,fnHandler){ if(oTarget.addEventListener){ oTarget.addEventListener(sEventType,fnHandler,false); }else if(oTarget.attachEvent){ oTarget.attachEvent("on"+sEventType,fnHandler); }else{ oTarget["on"+sEventType] = fnHandler; } }, //事件移除處理程序 removeEventHandler:function(oTarget,sEventType,fnHandler){ if(oTarget.removeEventListener){ oTarget.removeEventListener(sEventType,fnHandler,false); }else if(oTarget.detachEvent){ oTarget.detachEvent("on"+sEventType,fnHandler); }else{ oTarget["on"+sEventType] = null; } }, getEvent:function(event){ return event ? event : window.event; }, getTarget:function(event){ return event.target || event.srcElement; } }; /** *拖放程序 */ var Drag= Class.create(); Drag.prototype = { //初始化對象 initialize:function(drag,options){ this.Drag = $$(drag);//拖放對象 this._x = this._y = 0;//記錄鼠標相對于拖放對象的位置 //事件對象(用于綁定移除事件) this._fM = BindAsEventListener(this, this.Move); this._fS = Bind(this, this.Stop); this.Drag.style.position = "absolute"; this.marginLeft = this.marginTop = 0;//記錄margin //設置參數 this.setOptions(options); //獲取相關參數及類型轉換 this.Limit = !!this.options.Limit;//轉換為布爾型 this.mxLeft = parseInt(this.options.mxLeft); this.mxRight = parseInt(this.options.mxRight); this.mxTop = parseInt(this.options.mxTop); this.mxBottom = parseInt(this.options.mxBottom); this.Lock = !!this.options.Lock; this.LockX = !!this.options.LockX; this.LockY = !!this.options.LockY; this.onStart = this.options.onStart; this.onMove = this.options.onMove; this.onStop = this.options.onStop; this._Handle = $$(this.options.Handle) || this.Drag; this._mxContainer = $$(this.options.mxContainer) || null; //監聽拖動對象mousedown事件 EventUtil.addEventHandler(this.Drag, "mousedown", BindAsEventListener(this, this.Start)); }, //準備拖動 Start:function(oEvent){ if(this.Lock){return;}//如果鎖定則不執行 //記錄mousedown觸發時鼠標相對于拖放對象的位置 this._x = oEvent.clientX - this.Drag.offsetLeft; this._y = oEvent.clientY - this.Drag.offsetTop; //監聽mousemove 和 mouseup事件 EventUtil.addEventHandler(document, "mousemove", this._fM); EventUtil.addEventHandler(document, "mouseup", this._fS); }, //拖動 Move:function(oEvent){ //設置移動參數 var iLeft = oEvent.clientX - this._x , iTop = oEvent.clientY - this._y; //設置范圍限制 if(this.Limit){ //設置范圍參數 var mxLeft = this.mxLeft, mxRight = this.mxRight, mxTop = this.mxTop, mxBottom = this.mxBottom; //如果設置了容器，再修正范圍參數 if(!!this._mxContainer){ mxLeft = Math.max(mxLeft, 0); mxTop = Math.max(mxTop, 0); mxRight = Math.min(mxRight, this._mxContainer.clientWidth); mxBottom = Math.min(mxBottom, this._mxContainer.clientHeight); }; //修正移動參數 iLeft = Math.max(Math.min(iLeft, mxRight - this.Drag.offsetWidth), mxLeft); iTop = Math.max(Math.min(iTop, mxBottom - this.Drag.offsetHeight), mxTop); } //XY鎖定 if(!this.LockX)this.Drag.style.left = iLeft + "px"; if(!this.LockY)this.Drag.style.top = iTop + "px"; //執行附加程序 this.onMove(); }, //停止拖動 Stop:function(){ EventUtil.removeEventHandler(document, "mousemove", this._fM); EventUtil.removeEventHandler(document, "mouseup", this._fS); //執行附加程序 this.onStop(); }, //設置默認參數 setOptions:function(options){ this.options = {//默認值 Handle: "",//設置觸發對象（不設置則使用拖放對象） Limit: false,//是否設置范圍限制(為true時下面參數有用,可以是負數) mxLeft: 0,//左邊限制 mxRight: 9999,//右邊限制 mxTop: 0,//上邊限制 mxBottom: 9999,//下邊限制 mxContainer: "",//指定限制在容器內 LockX: false,//是否鎖定水平方向拖放 LockY: false,//是否鎖定垂直方向拖放 Lock: false,//是否鎖定 Transparent: false,//是否透明 onStart: function(){},//開始移動時執行 onMove: function(){},//移動時執行 onStop: function(){}//結束移動時執行 }; Extend(this.options, options || {}); } }; //初始化拖動對象 var drag = new Drag('drag',{mxContainer:'drag-wrap',Limit:true, onStart: function(){ $$("idShow").innerHTML = "開始拖放"; }, onMove: function(){ $$("idShow").innerHTML = "left："+this.Drag.offsetLeft+"；top:"+this.Drag.offsetTop; }, onStop: function(){ $$("idShow").innerHTML = "結束拖放"; } }); $$("idReset").onclick = function(){ drag.Limit = true; drag.mxLeft = drag.mxTop = 0; drag.mxRight = drag.mxBottom = 9999; drag.LockX = drag.LockY = drag.Lock = false; $$("idShow").innerHTML = "復位"; } $$("idLock").onclick = function(){ drag.Lock = true;$$("idShow").innerHTML = "鎖定全部";} $$("idLockX").onclick = function(){ drag.LockX = true; $$("idShow").innerHTML = "鎖定水平";} $$("idLockY").onclick = function(){ drag.LockY = true; $$("idShow").innerHTML = "鎖定垂直";} $$("idLimit").onclick = function(){ drag.mxRight = drag.mxBottom = 200;drag.Limit = true;$$("idShow").innerHTML = "范圍鎖定"; } $$("idLimitOff").onclick = function(){ drag.Limit = false; $$("idShow").innerHTML = "取消范圍鎖定";} </script></body></html>以上就是javascript實現拖放效果的代碼，希望對大家的學習有所幫助。
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