一个锁定层

/**
             * 创建一个遮盖层
             * id:遮盖层的id，如果为null，则自动生成一个id
             * cssObj:遮盖层的样式对象，也可以是一个类名
             * opacity:一个0-1之间的小数，表示透明度，数字越小透明度越高
             */
            function Lock(id,cssObj,opacity) {
                Lock.num=Lock.num||1;
                Lock.num++;
                //当前遮盖层的id
                var lockID = id ||'divlock_'+Lock.num;                
                //默认样式
                cssObj=cssObj||{backgroundColor:"black",filter:"alpha(Opacity=40)",opacity:"0.4",zIndex:"1"};
                if(opacity)
                    {
                        cssObj.opacity=opacity;
                        cssObj.filter="alpha(Opacity="+(opacity*100)+")";
                    }
                //一个getElementById的简写函数
                var $=function(id){document.getElementById(id);};
                //如果已经有同名的Dom元素,则返回此函数
                if($(id))
                {
                    this.success=false;
                    this.errorMsg='id重复';
                    return;
                }
                var divLock = document.createElement("div");
                //获取当前页面的高度
                var getBodyHeight= function ()
                {
                    //如果是IE
                    if(document.all)
                    {
                        return  Math.max(document.body.scrollHeight, document.documentElement.scrollHeight,document.documentElement.clientHeight);
                    }
                    return Math.max(document.body.scrollHeight, document.documentElement.scrollHeight);
                };
                divLock.id=lockID;
                divLock.style.width = Math.max(document.body.scrollWidth,document.documentElement.scrollWidth)+"px"
                divLock.style.height = getBodyHeight()+"px";
                divLock.style.position = "absolute";
                divLock.style.top = "0px";
                divLock.style.left = "0px";                
                divLock.style.display="none";                
                //divLock.style.verticalAlign="middle";               
                setClass(divLock,cssObj);               
                document.body.appendChild(divLock); 
                this.div=divLock;
                this.removed=false;
                this.show=function(){
                    if(this.removed)
                    {
                        return;
                    }
                    this.div.style.display="block";  
                };
                this.hidden=function(){
                    if(this.removed)
                    {
                        return;
                    }
                    this.div.style.display="none";  
                };
                this.remove=function(){
                    this.div.parentNode.removeChild(this.div);
                    this.removed=true;
                }
            }