js 用户填写非空验证
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<form action="index.html" method="get" onsubmit="return checkLogin()">
<p>用户名<input type="text" id="tv_uname"/><span id="tv_uname_span"></span></p>
<p>密码<input type="password" id="tv_upsw"/><span id="tv_upsw_span"></span></p>
<p><input type="submit" value="提交"/></p>
</form>
<script type="text/javascript">
function checkLogin(){
document.getElementById("tv_uname_span").innerHTML="";
document.getElementById("tv_upsw_span").innerHTML="";
var name = document.getElementById("tv_uname").value;
if(name==null||name==""){
document.getElementById("tv_uname_span").innerHTML="用户名不能空";
return false;
}
var psw = document.getElementById("tv_upsw").value;
if(psw==null||psw==""){
document.getElementById("tv_upsw_span").innerHTML="密码不能空";
return false;
}
return true;
}
</script>
</body>
</html>
js 省级联动
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<select onchange="show(this.value)">
<!--this.value就是index，也就是当前的value-->
<option value="0">北京市</option>
<option value="1">长沙市</option>
<option value="2">郴州市</option>
</select>
<select id="tv_select">
</select>
<script type="text/javascript">
var num = [["一区","二区","三区"],["4区","5区","6区"],["7区","8区","9区"]];
var select = document.getElementById("tv_select");
// select等于节点
function show(index){
var citys = num[index];
// citys等于三个区
var temp = "";
for(var i=0;i<citys.length;i++){
temp+="<option>"+citys[i]+"</option>";
// 三个区都在
}
select.innerHTML=temp;
// 三个区赋值给节点
}
</script>
</body>
</html>
js 输出最大值
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<form>
<p>数值1 <input type="text" class="s"</p>
<p>数值2 <input type="text" class="s"</p>
<p>数值3 <input type="text" class="s"</p>
<p>最大值 <input type="text" id="max"</p>
<p><input type="button" value="计算最大值" onclick="show()"</p>
</form>
<script type="text/javascript">
var sum = document.getElementsByClassName("s");
var temp = sum[0].value;
function show(){
for(var i=0;i<sum.length;i++){
if(temp<sum[i].value){
temp=sum[i].value;
}
}
document.getElementById("max").value=temp;
}
</script>
</body>
</html>
js练习 表单非空验证 省级联动 输出最大值