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)
        }
                    
    }