弹出js遮罩层

 <script type="text/javascript">

       var docEle = function() {

           return document.getElementById(arguments[0]) || false;

       }

       function openNewDiv(_id) {

           var m = "mask";

           if (docEle(_id)) document.body.removeChild(docEle(_id));

           if (docEle(m)) document.body.removeChild(docEle(m));

           //mask遮罩层

           var newMask = document.createElement("div");

           newMask.id = m;

           newMask.style.position = "absolute";

           newMask.style.zIndex = "1";

           _scrollWidth = Math.max(document.body.scrollWidth, document.documentElement.scrollWidth);

           _scrollHeight = Math.max(document.body.scrollHeight, document.documentElement.scrollHeight);

           newMask.style.width = _scrollWidth + "px";

           newMask.style.height = _scrollHeight + "px";

           newMask.style.top = "0px";

           newMask.style.left = "0px";

           newMask.style.background = "#33393C";

           newMask.style.filter = "alpha(opacity=40)";

           newMask.style.opacity = "0.40";

           document.body.appendChild(newMask);

           //新弹出层

           var newDiv = document.createElement("div");

           newDiv.id = _id;

           newDiv.style.position = "absolute";

           newDiv.style.zIndex = "9999";

           newDivWidth = 400;

           newDivHeight = 200;

           newDiv.style.width = newDivWidth + "px";

           newDiv.style.height = newDivHeight + "px";

           newDiv.style.top = (document.body.scrollTop + document.body.clientHeight / 2 - newDivHeight / 2) + "px";

           newDiv.style.left = (document.body.scrollLeft + document.body.clientWidth / 2 - newDivWidth / 2) + "px";

           newDiv.style.background = "#EFEFEF";

           newDiv.style.border = "1px solid #860001";

           newDiv.style.padding = "5px";

           newDiv.innerHTML = "弹出层内容 ";

           document.body.appendChild(newDiv);

           //弹出层滚动居中

           function newDivCenter() {

               newDiv.style.top = (document.body.scrollTop + document.body.clientHeight / 2 - newDivHeight / 2) + "px";

               newDiv.style.left = (document.body.scrollLeft + document.body.clientWidth / 2 - newDivWidth / 2) + "px";

           }

           if (document.all) {

               window.attachEvent("onscroll", newDivCenter);

           }

           else {

               window.addEventListener(\'scroll\', newDivCenter, false);

           }

           //关闭新图层和mask遮罩层

           var newA = document.createElement("a");

           newA.href = "#";

           newA.innerHTML = "关闭";

           newA.onclick = function() {

               if (document.all) {

                   window.detachEvent("onscroll", newDivCenter);

               }

               else {

                   window.removeEventListener(\'scroll\', newDivCenter, false);

               }

               document.body.removeChild(docEle(_id));

               document.body.removeChild(docEle(m));

               return false;

           }

           newDiv.appendChild(newA);

       }

</script>

调用<a onclick="openNewDiv(\'newDiv\');return false;" style="cursor:pointer">显示弹层</a>