<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>DOM event事件</title>
</head>
<body>
<!--1.ondblcilck-->
<!--<p ondblclick="alert(111)">11</p>-->
<!--onfocus 获得焦点-->
<input type="text" onfocus="f1()" onblur="f2()" value="please input your name" class="key_word">
<script>
function f1() {
var ke=document.getElementsByClassName('key_word');
ke[0].value=null;
}
function f2() {
var ke=document.getElementsByClassName('key_word');
if (ke[0].value.trim().length==0){//如果没有输入或者输入空格
ke[0].value="please input your name";
}
}
</script>
</body>
</html>