参考来源：
JavaScript基础语法-dom-bom-js-es6新语法-jQuery-数据可视化echarts黑马pink老师前端入门基础视频教程(500多集)持续_哔哩哔哩_bilibili
网页GitHub地址如下：（若加载较慢建议刷新后耐心等待一会~）
主要功能：
-
点击弹出模态框以及全屏灰色背景
-
点击关闭按钮，隐藏模态框以及背景
-
在模态框的头部按下鼠标开始移动，松开鼠标停止移动模态框
网页代码如下：
HTMLHTML+CSS+JS：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>js_login</title>
<style>
* {
margin: 0;
padding: 0;
}
a {
text-decoration: none;
color: #000;
}
.login {
display: none;
position: fixed;
top: 50%;
left: 50%;
width: 500px;
height: 218px;
border: 1px solid #ccc;
background-color: #fff;
transform: translate(-50%,-50%);
box-shadow: 0 0 20px #ddd;
z-index: 9999;
}
.login-header {
float: left;
width: 100%;
height: 100%;
line-height: 40px;
margin: 0 auto;
text-align: center;
font-weight: 700;
font-size: 16px;
color: #000;
}
.login-header a {
display: block;
margin: 0 auto;
}
.login-title {
cursor: move;
position: relative;
text-align: center;
font-size: 18px;
height: 40px;
line-height: 40px;
}
.login-title span{
position: absolute;
width: 40px;
height: 40px;
top: -20px;
right: -30px;
font-size: 12px;
border: 1px solid #ebebeb;
background-color: #fff;
border-radius: 50%;
}
.login-bd {
height: 108px;
}
.login-input {
float: right;
margin-right: 50px;
height: 50px;
line-height: 67px;
font-size: 12px;
}
input {
right: 50px;
border: 1px solid #ccc;
width: 370px;
height: 30px;
}
.login-btn {
margin: 15px 125px;
font-size: 12px;
width: 250px;
height: 30px;
line-height: 30px;
border: 1px solid #ccc;
text-align: center;
}
.login-bg {
display: none;
width: 100%;
height: 1000px;
background-color: gray;
z-index: 1;
}
</style>
</head>
<body>
<div id="login-header" class="login-header">
<a href="javascript:;">点击弹出登录框</a>
</div>
<div id="login" class="login">
<div class="login-title">登陆会员<span><a href="javascript:;" class="closebtn">关闭</a></span></div>
<div class="login-bd">
<div class="login-input">
<label>用户名：</label>
<input type="text" placeholder="请输入用户名" name="info[username]" id="username">
</div>
<div class="login-input">
<label>登陆密码：</label>
<input type="password" placeholder="请输入密码" name="info[password]" id="password">
</div>
</div>
<div id="login-btn" class="login-btn">
<a href="javascript:;">登录会员</a>
</div>
</div>
<div id="bg" class="login-bg"></div>
<script>
//1. 获取元素
var login = document.querySelector('.login');
var bg = document.querySelector('.login-bg');
var header = document.querySelector('.login-header');
var closebtn = document.querySelector('.closebtn');
var title = document.querySelector('.login-title');
//2. 注册事件
//2.1 点击弹出模态框以及全屏灰色背景
header.addEventListener('click',open);
function open() {
login.style.display = 'block';
bg.style.display = 'block';
};
//2.2 点击关闭按钮，隐藏模态框以及背景
closebtn.addEventListener('click',close);
function close() {
login.style.display = 'none';
bg.style.display = 'none';
}
//2.3 在模态框的头部按下鼠标开始移动，松开鼠标停止移动模态框
title.addEventListener('mousedown',function(e){
var x = e.pageX - login.offsetLeft;
var y = e.pageY - login.offsetTop;
document.addEventListener('mousemove',move);
function move(e) {
if((e.pageX - x) > 250 && (e.pageY - y) > 105){
login.style.left = e.pageX - x + 'px';
login.style.top = e.pageY - y + 'px';
}
}
document.addEventListener('mouseup',function() {
this.removeEventListener('mousemove',move);
})
});
</script>
</body>
</html>