<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
<script>
window.onload=function(){
function fun(){
var Ol=document.getElementById("text-name");
var Oin=document.getElementById("hello");
var Oform=document.getElementById("ceshi");
if(Ol.value.trim()==""){
var label=document.createElement("label")
label.setAttribute("for","text-name");
Oform.insertBefore(label,button);
Ol.labels[1].innerHTML="请输入您的姓名";
Ol.labels[1].setAttribute("style","font-size:9px;","color","blue")
}
}
}
</script>
</head>
<body>
<form id="ceshi">
<label id="nihao" for="text-name">姓名：</label>
<input id="text-name"/>
<input type="button" id="hello" value="验证" onClick="fun()">
</form>
</body>
</html>
button变量没有声明啊~
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
<script>
function fun(){
var Ol=document.getElementById("text-name");
var Oin=document.getElementById("hello");
var Oform=document.getElementById("ceshi");
if(Ol.value.trim()==""){
var label=document.createElement("label")
label.setAttribute("for","text-name");
Oform.insertBefore(label,Oin);
Ol.labels[1].innerHTML="请输入您的姓名";
Ol.labels[1].setAttribute("style","font-size:9px;","color","blue")
}
}
</script>
</head>
<body>
<form id="ceshi">
<label id="nihao" for="text-name">姓名：</label>
<input id="text-name"/>
<input type="button" id="hello" value="验证" onClick="fun()">
</form>
</body>
</html>写在onload可以
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
<script>
window.onload=function(){
var Ol=document.getElementById("text-name");
var Oin=document.getElementById("hello");
var Oform=document.getElementById("ceshi");
function fun(){
if(Ol.value.trim()==""){
var label=document.createElement("label")
label.setAttribute("for","text-name");
Oform.insertBefore(label,Oin);
Ol.labels[1].innerHTML="请输入您的姓名";
Ol.labels[1].setAttribute("style","font-size:9px;","color","blue")
}
}
Oin.addEventListener("click",fun,this);
}
</script>
</head>
<body>
<form id="ceshi">
<label id="nihao" for="text-name">姓名：</label>
<input id="text-name"/>
<input type="button" id="hello" value="验证" >
</form>
</body>
</html>