html选择区域高亮 css+js实现部分区域高亮可编辑遮罩层

想大家都做过遮罩层这种常见的功能，css或jquery实现，实现方式多样化，这里http://我介绍我在项目中实现的方式，全屏遮罩，部分区域可操作，非常实用。

效果如下图：

js 实现部分：

var myAlert = document.getElementById("alert");

var reg = document.getElementById("content").getElementsByTagName("a")[0];

reg.onclick = function() {

myAlert.style.background = "#e2ecf5";

myAlert.style.zIndex = "501";

myAlert.style.position = "absolute";

var signSpan = document.getElementById("signSpanId");

myAlert.style.top = signSpan.offsetTop;

myAlert.style.left = signSpan.offsetLeft;

mybg = document.createElement("div");

mybg.setAttribute("id", "mybg");

mybg.style.background = "#000";

mybg.style.width = "100%";

mybg.style.height = "100%";

mybg.style.position = "absolute";

mybg.style.top = "0";

mybg.style.left = "0";

mybg.style.zIndex = "500";

mybg.style.opacity = "0.3";

mybg.style.filter = "Alpha(opacity=30)";

document.body.appendChild(mybg);

//document.body.style.overflow = "hidden";

}

页面代码：