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来源：4-11 编程练习

localhost999

2021-09-20 17:18:41

<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title>onblur和onfocus</title>
    <style type="text/css">
        .red{
    		border:1px solid red;
    	}
    </style>
</head>
<body>
	<div>
		姓名：<input type="text"> <span></span>
	</div>
	<script type="text/javascript">
		var kuan=document.getElementsByTagName('input');
		var x =document.getElementsByTagName('span');
		kuan[0].onfocus=function(){
			var x =document.getElementsByTagName('span');
			x[0].innerText="请输入姓名";
		};

		kuan[0].onblur=function(){
			if(kuan[0].value==""){
				x[0].innerText="用户名不能为空";
				kuan[0].style.border="1px red solid";
			} else{
				x[0].innerText="";
				kuan[0].style.border="";

			}
		}
	</script>
</body>
</html>

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