<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>MyHtml.html</title> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="this is my page"> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> <!--<link rel="stylesheet" type="text/css" href="./styles.css">--> </head> <script type="text/javascript"> function selectshi(sheng){ var s = sheng.value; var shi = document.getElementById("shi"); if(s == 'initial'){ shi.innerHTML = '<option>请选择市</option>'; }else if(s == 'bj'){ shi.innerHTML = '<option>朝阳区</option><option>海淀区</option>'; }else if(s == 'hb'){ shi.innerHTML = '<option>石家庄</option><option>张家界</option><option>保定</option>'; }else if(s == 'ln'){ shi.innerHTML = '<option>沈阳</option><option>大连</option><option>营口</option>'; }else if(s == 'hn'){ shi.innerHTML = '<option>郑州</option><option>洛阳</option><option>焦作</option>'; }else if(s == 'js'){ shi.innerHTML = '<option>南京</option><option>徐州</option><option>苏州</option>'; } } </script> <body> <select id="sheng" onchange="selectshi(this)"> <option value="initial">请选择省</option> <option value="bj">北京市</option> <option value="sd">山东省</option> <option value="hb">河北省</option> <option value="ln">辽宁省</option> <option value="hn">河南省</option> <option value="js">江苏省</option> </select> <select id="shi"> <option>请选择市</option> </select><br> </body></html> function selectshi(sheng ){
var obj=document.getElementById("shi");
obj.options.length=0;
var s = sheng.value;
if(s == 'initial') {
obj.options.add(new Option('Please select city',''));
}else if(s=='bj'){
obj.options.add(new Option ('Chaoyang District','cy'));
obj.options.add(new Option('Haidian District','hd'));
}else if(s==hb){
obj.options.add(new Option('Shijiazhuang','sjz'));
obj.options.add(new Option('Zhangjiajie','zjj'));
}else if(s =='ln'){
.....
}
}
or:
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
