js+html achieves mask layer effect

//遮罩  
    function coverDiv(){  
        var procbg = document.createElement("div"); //首先创建一个div  
        procbg.setAttribute("id","mybg"); //定义该div的id  
        procbg.style.background = "#000000";  
        procbg.style.width = "100%";  
        procbg.style.height = "100%";  
        procbg.style.position = "fixed";  
        procbg.style.top = "0";  
        procbg.style.left = "0";  
        procbg.style.zIndex = "500";  
        procbg.style.opacity = "0.6";  
        procbg.style.filter = "Alpha(opacity=70)";  
        document.body.appendChild(procbg);  
    }  
    //取消遮罩  
    function hide() {  
        /* document.getElementById('light').style.display="none"; */ 
        $("div[class='xucun_content']").hide();  
        var body = document.getElementsByTagName("body");  
        var mybg = document.getElementById("mybg");  
        body[0].removeChild(mybg);  
    }