[1.1在html中](1.1%E5%9C%A8html%E4%B8%AD.md) [1.2在js中](1.2%E5%9C%A8js%E4%B8%AD.md) [1.3设置默认项](1.3%E8%AE%BE%E7%BD%AE%E9%BB%98%E8%AE%A4%E9%A1%B9.md)