文字滚动的js函数

//scrollBodyId:	String 内部滚动div的id
//scrollBoxId:	String 外面限制div的id
//showHeight:	Int 限制显示高度
//showWidth:	Int 限制显示宽度
//lineHeight:	Int 每行的高度
//stopTime:     Int 间隔停止的时间（毫秒）
//speed:	    Int 滚动速度（毫秒，越小越快）
var ScrollObj = function(scrollBodyId,scrollBoxId,showHeight,showWidth,lineHeight,stopTime,speed) {
	this.obj = document.getElementById(scrollBodyId);
	this.box = document.getElementById(scrollBoxId);
	
	this.style = this.obj.style;
	this.defaultHeight = this.obj.offsetHeight;
	
	this.obj.innerHTML += this.obj.innerHTML;
	this.obj.style.position = "relative";
	
	this.box.style.height = showHeight;
	this.box.style.width = showWidth;
	this.box.style.overflow = "hidden";
	
	this.scrollUp = doScrollUp;

	this.stopScroll = false;
	
	this.curLineHeight = 0;
	this.lineHeight = lineHeight;
	this.curStopTime = 0;
	this.stopTime = stopTime;
	this.speed = speed;

	this.style.top = lineHeight;

	this.object = scrollBodyId + "Object";
	eval(this.object + "=this");
	setInterval(this.object+".scrollUp()",speed);
	this.obj.onmouseover=new Function(this.object+".stopScroll=true");
	this.obj.onmouseout=new Function(this.object+".stopScroll=false");
}
function doScrollUp(){
	if( this.stopScroll == true )
		return;
  	this.curLineHeight += 1;
  	if( this.curLineHeight >= this.lineHeight ){
  		this.curStopTime += 1;
  		if( this.curStopTime >= this.stopTime ){
  			this.curLineHeight = 0;
  			this.curStopTime = 0;
  		}
  	}
	else{  	
	  	this.style.top = parseInt(this.style.top) - 1;
	  	if( -parseInt(this.style.top) >= this.defaultHeight ){
	    	this.style.top = 0;
	  	}
  	}
}