jQuery的安装
1.共有两个版本的 jQuery 可供下载：
- Production version - 用于实际的网站中，已被精简和压缩。
- Development version - 用于测试和开发（未压缩，是可读的代码）
这两个版本都可从 https://jquery.com/download/下载。
<head> <script src="jquery.js"></script> </head>
2.网络引用【无需下载】
不下载并存放 jQuery，可以通过 CDN（内容分发网络） 引用它。
谷歌和微软的服务器都存有 jQuery 。
谷歌：
<head> <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.0/jquery.min.js"> </script> </head>
微软：
<head> <script src="https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.4.1.min.js"></script> </head>
https://docs.microsoft.com/en-us/aspnet/ajax/cdn/overview#jQuery_Releases_on_the_CDN_0
jQuery在微软CDN上发布 以下版本的jQuery托管在CDN上： jQuery版本3.4.1 https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.4.1.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.4.1.min.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.4.1.min.map https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.4.1.slim.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.4.1.slim.min.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.4.1.slim.min.map jQuery版本3.4.0 https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.4.0.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.4.0.min.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.4.0.min.map https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.4.0.slim.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.4.0.slim.min.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.4.0.slim.min.map jQuery版本3.3.1 https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.3.1.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.3.1.min.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.3.1.min.map https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.3.1.slim.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.3.1.slim.min.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.3.1.slim.min.map jQuery版本3.2.1 https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.2.1.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.2.1.min.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.2.1.min.map https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.2.1.slim.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.2.1.slim.min.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.2.1.slim.min.map jQuery版本3.2.0 https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.2.0.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.2.0.min.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.2.0.min.map https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.2.0.slim.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.2.0.slim.min.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.2.0.slim.min.map jQuery版本3.1.1 https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.1.1.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.1.1.min.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.1.1.min.map https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.1.1.slim.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.1.1.slim.min.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.1.1.slim.min.map jQuery版本3.1.0 https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.1.0.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.1.0.min.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.1.0.min.map https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.1.0.slim.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.1.0.slim.min.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.1.0.slim.min.map jQuery版本3.0.0 https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.0.0.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.0.0.min.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.0.0.min.map https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.0.0.slim.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.0.0.slim.min.js https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.0.0.slim.min.map
还有其他
使用谷歌或微软的 jQuery，有一个很大的优势：
许多用户在访问其他站点时，已经从谷歌或微软加载过 jQuery。所有结果是，当他们访问您的站点时，会从缓存中加载 jQuery，这样可以减少加载时间。同时，大多数 CDN 都可以确保当用户向其请求文件时，会从离用户最近的服务器上返回响应，这样也可以提高加载速度。
