jquery实现文件单个下传,区分类型

jquery实现文件单个上传,区分类型?
[code="java"

<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
        <title>信息列表</title>
        <script type="text/javascript" src="jquery-1.4.4.min.js">
        </script>
        <script>
          
                  function info(form) {
              var optr = $("#select").val();
                    var type = $("#shortPic").val().split(".");
                        type = type[type.length-1];
   form.reset();
                    if(optr == "") {
                    alert("请选择上传类型!");
                    return false;
                    }
if(type == "") {
                    alert("请选择上传文件!");
                    return false;
                    }
            if(optr == 1 && type !="html"){
            alert("请选择html格式网页文件");
//document.getElementById("shortPic").value = "";
//alert(document.getElementById("shortPic").value);
            return false;
                }
if(optr == 2 && type !="jpg"){
alert("请请选择jpg格式图片文件");
return false;
}
if(optr ==3 && (type !="mp3" && type != "wav")){
alert("请选择3gp或mav格式的视频文件");
return false;
}

if(optr ==4 &&(type !="doc" && type !="ppt")){
alert("请选择doc或ppt格式文档文件");
return false;

}
if(optr==4 &&(type !="doc" && type !="text" && type !="pdf")){
alert("请选择doc或者text或者pdf格式资料文件");
return false;
}
alert("上传成功");
              }
 
             
           
               
        </script>
        <body>
            <form onsubmit="return info(this)" action="#" method="post" enctype="multipart/form-data">
                <select id="select">
                    <option value="0">--请选择--</option>
                    <option value="1">网页</option>
                    <option value="2">图片</option>
                    <option value="3">视频</option>
                    <option value="4">档案</option>
                    <option value="5">资料</option>
                </select>
                <input type="file" name="shortPic" value="" id="shortPic" />
                <br/>
                <input type="submit" value="submit" id="shortPic1"/>
            </form>
        </body>
        </html>
]