<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
*{
margin: 0;
}
#div1{
position: fixed;
width: 100%;
top: 0;
left: 0;
height: 2000px;
background-color: #b4b4b4;
z-index: 1000;
}
#div2{
position: fixed;
width: 100%;
z-index: 1001;
top: 0;
left: 0;
right: 0;
bottom: 0;
background-color: red;
opacity: 0.1;
}
#div3{
height: 200px;
width: 200px;
background-color: blueviolet;
position: absolute;
top: 50%;
left: 50%;
z-index: 1002;
margin-left: -100px;
margin-top: -100px;
}
.hide{
display: none;
}
</style>
</head>
<body>
<div id="div1" >
<input type="button" value="click" onclick="show()">
</div>
<div id="div2" class="div hide"></div>
<div id="div3" class="div hide">
<input type="button" value="cancel" onclick="cancel()">
</div>
<script>
function show() {
var ele=document.getElementsByClassName("div")
for (var i=0;i<ele.length;i++){
ele[i].classList.remove("hide")
}
}
function cancel() {
var ele=document.getElementsByClassName("div")
for (var i=0;i<ele.length;i++){
ele[i].classList.add("hide")
}
}
</script>
</body>
</html>
原文：https://www.cnblogs.com/gerenboke/p/11771326.html