<SCRIPT language="JavaScript">

<!-- Hide script from older browsers

extArray = new Array(".gif", ".jpg", ".png");

function LimitAttach(form, file) {

allowSubmit = false;

if (!file) return;

while (file.indexOf("\") != -1)

file = file.slice(file.indexOf("\") + 1);

ext = file.slice(file.indexOf(".")).toLowerCase();

for (var i = 0; i < extArray.length; i++) {

if (extArray[i] == ext) { allowSubmit = true; break; }

}

if (allowSubmit) form.submit();

else

alert("Please only upload files that end in types:  "

+ (extArray.join("  ")) + "nPlease select a new "

+ "file to upload and submit again.");

}

//  End -->

</script>

<form method="POST" action="newphoto.asp" enctype="multipart/form-data" id=form1 name=form1>

<input type="file" name="UploadForm" size="30"><BR><BR>

<input type="button" name="submit" value="Upload Your Photo!" onclick="LimitAttach(this.form, this.form.UploadForm.value)">

———————————————————

<form onsubmit= "return a(this) ">

<input type=file name=f>

<input type=submit>

</form>

<input type="file" onchange="checkExt(this)"/>

<script >
var checkExt=function(file) {
    if(!(/(?:jpg|gif)$/i.test(file.value))) {
        alert("只允许上传jpg和gif的图片");
        if(window.ActiveXObject) {//for IE
            file.select();//select the file ,and clear selection
            document.selection.clear();
        } else if(window.opera) {//for opera
            file.type="text";file.type="file";
        } else file.value="";//for FF,Chrome,Safari
    } else {
        alert("ok");//or you can do nothing here.
    }
};
</script>