js遮罩层弹出显示效果组件化

1.在web开发中经常遇到遮罩层的效果，可以将这种常用方法通用化

     function showid(idname){
         var isIE = (document.all) ? true : false;
         var isIE6 = isIE && ([/MSIE (\d)\.0/i.exec(navigator.userAgent)][0][1] == 6);
         var newbox = document.getElementById(idname);
         newbox.style.zIndex = "9999999";
         newbox.style.display = "block"
         newbox.style.position = !isIE6 ? "fixed" : "absolute";
         newbox.style.top = newbox.style.left = "50%";
         newbox.style.marginTop = -newbox.offsetHeight / 2 + "px";
         newbox.style.marginLeft = -newbox.offsetWidth / 2 + "px";
         var layer = document.createElement("div");
         layer.id = "layer";
         layer.style.width = layer.style.height = "100%";
         layer.style.position = !isIE6 ? "fixed" : "absolute";
         layer.style.top = layer.style.left = 0;
         layer.style.backgroundColor = "#888";
         layer.style.zIndex = "9999998";
         layer.style.opacity = "0.6";
         document.body.appendChild(layer);

         function layer_iestyle(){
             layer.style.width = Math.max(document.documentElement.scrollWidth, document.documentElement.clientWidth) +
             "px";
             layer.style.height = Math.max(document.documentElement.scrollHeight, document.documentElement.clientHeight) +
             "px";
         }
         function newbox_iestyle(){
             newbox.style.marginTop = document.documentElement.scrollTop - newbox.offsetHeight / 2 + "px";
             newbox.style.marginLeft = document.documentElement.scrollLeft - newbox.offsetWidth / 2 + "px";
         }
         if (isIE) {
             layer.style.filter = "alpha(opacity=60)";
         }
         if (isIE6) {
             layer_iestyle()
             newbox_iestyle();
             window.attachEvent("onscroll", function(){
                 newbox_iestyle();
             })
             window.attachEvent("onresize", layer_iestyle)
         }

     }