js一个取值的问题！懂JS的请进指教！
<script type="text/javascript">  
 
function CLASS_MSN_MESSAGE(id,width,height,caption,title,message,target,action){  
   
  this.id = id;  
  this.title = title;  
  this.caption= caption;  
  this.message= message;
  this.target = target;  
  this.action = action;  
  this.width = width?width:200;  
  this.height = height?height:120;  
  this.timeout= 150;  
  this.speed = 20; 
  this.step = 1; 
  this.right = screen.width -1;  
  this.bottom = screen.height; 
  this.left = this.right - this.width; 
  this.top = this.bottom - this.height; 
  this.timer = 0; 
  this.pause = false;
  this.close = false;
  this.autoHide = true;
}  
  
/**//*  
* 隐藏消息方法  
*/  
CLASS_MSN_MESSAGE.prototype.hide = function(){  
  if(this.onunload()){  
  var offset = this.height>this.bottom-this.top?this.height:this.bottom-this.top; 
  var me = this;  
  if(this.timer>0){  
  window.clearInterval(me.timer);  
  }  
  var fun = function(){  
  if(me.pause==false||me.close){
  var x = me.left; 
  var y = 0; 
  var width = me.width; 
  var height = 0; 
  if(me.offset>0){ 
  height = me.offset; 
  } 
   
  y = me.bottom - height; 
   
  if(y>=me.bottom){ 
  window.clearInterval(me.timer);  
  me.Pop.hide();  
  } else { 
  me.offset = me.offset - me.step;  
  } 
  me.Pop.show(x,y,width,height);  
  }  
  }  
  this.timer = window.setInterval(fun,this.speed)  
  }  
}  
  
/**//*  
* 消息卸载事件，可以重写  
*/  
CLASS_MSN_MESSAGE.prototype.onunload = function() {  
  return true;  
}  
/**//*  
* 消息命令事件，要实现自己的连接，请重写它  
*  
*/  
CLASS_MSN_MESSAGE.prototype.oncommand = function(){  
  //this.close = true;
  this.hide();  
 window.open("http://www.cnquanji.com");
   
} 
/**//*  
* 消息显示方法  
*/  
CLASS_MSN_MESSAGE.prototype.show = function(){  
  var oPopup = window.createPopup(); //IE5.5+  
   
  this.Pop = oPopup;  
  
  var w = this.width;  
  var h = this.height;  
  
  var str = "<DIV style='BORDER-RIGHT: #455690 1px solid; BORDER-TOP: #a6b4cf 1px solid; Z-INDEX: 99999; LEFT: 0px; BORDER-LEFT: #a6b4cf 1px solid; WIDTH: " + w + "px; BORDER-BOTTOM: #455690 1px solid; POSITION: absolute; TOP: 0px; HEIGHT: " + h + "px; BACKGROUND-COLOR: #c9d3f3'>"  
  str += "<TABLE style='BORDER-TOP: #ffffff 1px solid; BORDER-LEFT: #ffffff 1px solid' cellSpacing=0 cellPadding=0 width='100%' bgColor=#cfdef4 border=0>"