function stopDefault(e) {// 绂佹娴忚鍣ㄩ粯璁よ涓
	var e= e || event;
	if (e.preventDefault) {
		e.preventDefault();
	} else {
		window.event.returnValue = false;
	}

	return false;
}

//妯℃嫙婊氬姩鏉
function ImitateScroll(scrollBox, scrollObj, scrollBar, scrollBtn)
{//scrollBox琚粴鍔ㄥ璞″妗嗭紝scrollObj琚粴鍔ㄥ璞★紝scrollBar婊氬姩鏉″潡锛屾粴鍔ㄦ潯鎸夐挳
	this.init(scrollBox, scrollObj, scrollBar, scrollBtn);
}

ImitateScroll.prototype = {
	scale:function() {//琚粴鍔ㄥ璞′笌琚粴鍔ㄥ璞″妗嗙殑楂樺害姣斾緥璁＄畻
		return (this.scrollObj.scrollHeight/this.scrollBox.clientHeight);
	},
	scrollBtnMouseDown:function(ev) {//婊氬姩鎸夐挳鎸変笅
		var _this = this;
		var disY = ev.clientY - this.scrollBtn.offsetTop;//榧犳爣Y鍧愭爣璺濈婊氬姩鎸夐挳澶撮儴鐨勮窛绂
		var maxTop =  this.scrollBar.clientHeight - this.scrollBtn.offsetHeight;

		document.onmousemove = function(ev) {
			if (document.all) {//ie 绂佹閫夋嫨
				document.body.onselectstart = new Function("return false");
			} else {// chrome, ff
				document.body.className = "chromeOnselectstart";
			}

			var oEvent = ev || event;
			var t = oEvent.clientY - disY;
			t = t>maxTop ? maxTop : t;
			t = t<0 ? 0 : t;

			 _this.scrollBtn.style.top = t + "px";
			 //_this.scrollObj.style.top = -t / _this.scrollBar.clientHeight * _this.scrollObj.scrollHeight + "px";
			  _this.scrollObj.style.top = -t / (_this.scrollBar.clientHeight-_this.scrollBtn.offsetHeight) * (_this.scrollObj.scrollHeight-_this.scrollBox.clientHeight) + "px";
		};
		document.onmouseup = function() {
			if (document.all) {//ie 瑙ｉ櫎绂佹閫夋嫨
				document.body.onselectstart = new Function("return true");
			} else {// chrome, ff
				document.body.className = "";
			}

			document.onmousemove = document.onmouseup = null;//娓呴櫎move鍜寀p浜嬩欢
		};
	},
	scrollBoxMousewheel:function(ev) {//榧犳爣婊氳疆婊氬姩
		var direct = 0;
		var topCur = this.scrollBtn.offsetTop;
		var maxTop =  this.scrollBar.clientHeight - this.scrollBtn.offsetHeight;
		//婊氳疆姣忔婊氬姩锛屾粴鍔ㄦ寜閽璧扮殑璺濈锛屾祴璇昪hrome婊?娆″樊涓嶅涓€灞
		var directTop = this.scrollBox.clientHeight / 8 / this.scrollObj.scrollHeight * this.scrollBar.clientHeight;
		directTop = directTop>0 ? Math.ceil(directTop) : Math.floor(directTop);

		stopDefault(ev);//绂佹娴忚鍣ㄨ嚜韬殑婊氬姩鏉℃粴鍔ㄦ晥鏋
		if (ev.wheelDelta)  {//IE/Opera/Chrome 
			direct = ev.wheelDelta;
		} else if (ev.detail) {//Firefox 
			direct = ev.detail * (-1);
		}

		if(parseFloat(direct) > 0) {
			var topEnd = topCur - directTop;
			if (topEnd < 0) {topEnd = 0;}
		} else {
			var topEnd = topCur + directTop;
			topEnd = topEnd>maxTop ? maxTop : topEnd;
		}

		this.scrollBtn.style.top = topEnd + "px";
		//this.scrollObj.style.top = -topEnd / this.scrollBar.clientHeight * this.scrollObj.scrollHeight + "px";
		this.scrollObj.style.top = -topEnd / (this.scrollBar.clientHeight-this.scrollBtn.offsetHeight) * (this.scrollObj.scrollHeight-this.scrollBox.clientHeight) + "px";
	},
	init:function(scrollBox, scrollObj, scrollBar, scrollBtn) {//鍒濆鍖
		this.scrollBox = typeof scrollBox == "string" ? document.getElementById(scrollBox) : scrollBox;
		this.scrollObj = typeof scrollObj == "string" ? document.getElementById(scrollObj) : scrollObj;
		this.scrollBar = typeof scrollBar == "string" ? document.getElementById(scrollBar) : scrollBar;
		this.scrollBtn = typeof scrollBtn == "string" ? document.getElementById(scrollBtn) : scrollBtn;
		var scale = this.scale();////琚粴鍔ㄥ璞′笌琚粴鍔ㄥ璞″妗嗙殑楂樺害姣斾緥

		if (scale <= 1) {//鍒ゆ柇鏄惁杈惧埌浜х敓婊氬姩鏉＄殑鏉′欢
			// this.scrollObj.style.width   = "100%";
			this.scrollBar.style.display = "none";
			return;
		} else {
			// this.scrollObj.style.width   = "95%";
			this.scrollBar.style.display = "block";
		}

		// if(_this.scrollObj.scrollHeight+_this.scrollObj.offsetTop < _this.scrollBox.clientHeight)
		// {//鍒ゆ柇琚粴鍔ㄥ璞℃槸鍚︽粴杩囧ご浜
		// 	 _this.scrollObj.style.top = _this.scrollBox.clientHeight-_this.scrollObj.scrollHeight+"px";
		// }

		//鍒濆鍖栨粴鍔ㄦ寜閽殑楂樺害鍜宼op鍊
		//this.scrollBtn.style.height = 20 + "px"; //璁惧畾婊氬姩鎸夐挳鐨勯珮搴
		//this.scrollBtn.style.top = -this.scrollObj.offsetTop/this.scrollObj.scrollHeight*this.scrollBar.clientHeight + "px";

		var _this = this;
		this.scrollBtn.onmousedown = function(e) {//婊氬姩鎸夐挳鎷栨嫿浜嬩欢
			var e = e || event;
			_this.scrollBtnMouseDown(e);
		};

		//缁戝畾婊氳疆浜嬩欢
		if (this.scrollBox.addEventListener) {//ff3.5浠ヤ笅
			this.scrollBox.addEventListener("DOMMouseScroll", function(e) {
				var e = e || event;
				_this.scrollBoxMousewheel(e)
			}, false);
		}
		//W3C
		this.scrollBox.onmousewheel = function(e) {
			var e = e || event;
			_this.scrollBoxMousewheel(e)
		}; //IE/Opera/Chrome
	}
}