<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>拖放效果</title>
</head>
<body>
<script> 
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 Bind = function(object, fun) {
 return function() {
  return fun.apply(object, arguments);
 }
}
var BindAsEventListener = function(object, fun) {
 return function(event) {
  return fun.call(object, (event || window.event));
 }
}
var CurrentStyle = function(element){
 return element.currentStyle || document.defaultView.getComputedStyle(element, null);
}
function addEventHandler(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;
 }
};
function removeEventHandler(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;
 }
};
//拖放程序
var Drag = Class.create();
Drag.prototype = {
//拖放對象
 initialize: function(drag, options) {
 this.Drag = $(drag);//拖放對象
 this._x = this._y = 0;//記錄鼠標相對拖放對象的位置
 this._marginLeft = this._marginTop = 0;//記錄margin
 //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.SetOptions(options);
 this.Limit = !!this.options.Limit;
 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.LockX = !!this.options.LockX;
 this.LockY = !!this.options.LockY;
 this.Lock = !!this.options.Lock;
 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;
 this.Drag.style.position = "absolute";
 //透明
 if(isIE && !!this.options.Transparent){
  //填充拖放對象
  with(this._Handle.appendChild(document.createElement("div")).style){
   width = height = "100%"; backgroundColor = "#fff"; filter = "alpha(opacity:0)";
  }
 }
 //修正范圍
 this.Repair();
 addEventHandler(this._Handle, "mousedown", BindAsEventListener(this, this.Start));
 },
 //設置默認屬性
 SetOptions: function(options) {
 this.options = {//默認值
  Handle:   "",//設置觸發(fā)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(shù)有用,可以是負數(shù))
  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(nèi)
  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(zhí)行
  onMove:   function(){},//移動時執(zhí)行
  onStop:   function(){}//結束移動時執(zhí)行
 };
 Extend(this.options, options || {});
 },
 //準備拖動
 Start: function(oEvent) {
 if(this.Lock){ return; }
 this.Repair();
 //記錄鼠標相對拖放對象的位置
 this._x = oEvent.clientX - this.Drag.offsetLeft;
 this._y = oEvent.clientY - this.Drag.offsetTop;
 //記錄margin
 this._marginLeft = parseInt(CurrentStyle(this.Drag).marginLeft) || 0;
 this._marginTop = parseInt(CurrentStyle(this.Drag).marginTop) || 0;
 //mousemove時移動 mouseup時停止
 addEventHandler(document, "mousemove", this._fM);
 addEventHandler(document, "mouseup", this._fS);
 if(isIE){
  //焦點丟失
  addEventHandler(this._Handle, "losecapture", this._fS);
  //設置鼠標捕獲
  this._Handle.setCapture();
 }else{
  //焦點丟失
  addEventHandler(window, "blur", this._fS);
  //阻止默認動作
  oEvent.preventDefault();
 };
 //附加程序
 this.onStart();
 },
 //修正范圍
 Repair: function() {
 if(this.Limit){
  //修正錯誤范圍參數(shù)
  this.mxRight = Math.max(this.mxRight, this.mxLeft + this.Drag.offsetWidth);
  this.mxBottom = Math.max(this.mxBottom, this.mxTop + this.Drag.offsetHeight);
  //如果有容器必須設置position為relative來相對定位，并在獲取offset之前設置
  !this._mxContainer || CurrentStyle(this._mxContainer).position == "relative" || (this._mxContainer.style.position = "relative");
 }
 },
 //拖動
 Move: function(oEvent) {
 //判斷是否鎖定
 if(this.Lock){ this.Stop(); return; };
 //清除選擇
 window.getSelection ? window.getSelection().removeAllRanges() : document.selection.empty();
 //設置移動參數(shù)
 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(shù)
  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(shù)
  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(shù)
  iLeft = Math.max(Math.min(iLeft, mxRight - this.Drag.offsetWidth), mxLeft);
  iTop = Math.max(Math.min(iTop, mxBottom - this.Drag.offsetHeight), mxTop);
 }
 //設置位置，并修正margin
 if(!this.LockX){ this.Drag.style.left = iLeft - this._marginLeft + "px"; }
 if(!this.LockY){ this.Drag.style.top = iTop - this._marginTop + "px"; }
 //附加程序
 this.onMove();
 },
 //停止拖動
 Stop: function() {
 //移除事件
 removeEventHandler(document, "mousemove", this._fM);
 removeEventHandler(document, "mouseup", this._fS);
 if(isIE){
  removeEventHandler(this._Handle, "losecapture", this._fS);
  this._Handle.releaseCapture();
 }else{
  removeEventHandler(window, "blur", this._fS);
 };
 //附加程序
 this.onStop();
 }
};
</script>
<style> 
#idContainer{ border:10px solid #990000; width:600px; height:300px;}
#idDrag{ border:5px solid #C4E3FD; background:#C4E3FD; width:50px; height:50px; top:50px; left:50px;}
#idHandle{cursor:move; height:25px; background:#0000FF; overflow:hidden;}
</style>
<div id="idContainer">
<div id="idDrag"><div id="idHandle"></div></div>
</div>
<input id="idReset" type="button" value="復位" />
<input id="idLock" type="button" value="鎖定" />
<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(tài)：<span id="idShow">未開始</span>
<script> 
var drag = new Drag("idDrag", { mxContainer: "idContainer", Handle: "idHandle", 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;
}
$("idLock").onclick = function(){ drag.Lock = true; }
$("idLockX").onclick = function(){ drag.LockX = true; }
$("idLockY").onclick = function(){ drag.LockY = true; }
$("idLimit").onclick = function(){  drag.mxRight = drag.mxBottom = 200;drag.Limit = true; }
$("idLimitOff").onclick = function(){ drag.Limit = false; }
</script>
</body>
</html>

希望本文所述對大家JavaScript程序設計有所幫助。

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