<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
<script type="text/javascript">
function al(){
var x=document.getElementById("d1");
var zhi=x.value;//img.jpg
var hou=zhi.lastIndexOf(".");//找到点的位置
var k=zhi.search(hou+1);//点的位置往后挪一个位置
var k=k.toLowerCase;//都降为小写
if(k =="jpg"||k =="png"||k =="gif"){
document.write("成功");
}else{
document.write("失败");
}
}
</script>
</head>
<body>
<input type="file" id="d1">
<input type="button" id="d2" value="点击上传" onclick="al()">
</body>
</html>