如何限制上传附件的格式？

<script type="text/javascript">
        $(document).ready(function() {
            //$("#name").focus();
            var id=$("#id").val();
            if(id!=""){
                $("#policeNo").attr("readonly","readonly")//
            }    
            $("#inputForm").validate({
                submitHandler: function(form){
                    loading(‘正在提交，请稍等...‘);
                    form.submit();
                },
                errorContainer: "#messageBox",
                errorPlacement: function(error, element) {
                    $("#messageBox").text("输入有误，请先更正。");
                    if (element.is(":checkbox")||element.is(":radio")||element.parent().is(".input-append")){
                        error.appendTo(element.parent().parent());
                    } else {
                        error.insertAfter(element);
                    }
                }
            });            
              $("#uploadFile").live("change",function () {
                    var filepath = $("input[name=‘uploadFile‘]").val();
                    var extStart = filepath.lastIndexOf(".");
                    var ext = filepath.substring(extStart, filepath.length).toUpperCase()
                    /* if(ext == "" or ext == null){
                        art.dialog.alert("请上传签字图片！");
                        return false;
                    } */
                    if( ext != "" && ext != ".BMP" && ext != ".PNG" && ext != ".GIF" && ext != ".JPG" && ext != ".JPEG") {
                        art.dialog.alert("图片限于bmp,png,gif,jpeg,jpg格式,且大小不能超过10M");
                        $("#uploadFile").remove();
                        $("#pic_add").append("<input id=‘uploadFile‘ type=‘file‘ name=‘uploadFile‘
 accept=".png,.jpg,.gif,.jpeg,.ico,.bmp"/>");
                        return false;
                    } 
              });      
        });
    </script>