我想在提交最终的 sibmit 按钮 saveBank(） 之前验证上传按钮

我想在提交saveBank()按钮之前验证上传按钮。在发送表单之前，必须在预览图像后验证文件上传按钮以进行单击。

<form id="panCopyUp" action="" method="post" enctype="multipart/form-data" class="form-horizontal">
    <div class="form-group">
        <label style="padding-left: 153px;" for="ben" class="control-label col-md-4">Upload PAN Register Copy * :</label>
        <input style="margin-top: 9px; margin-left: 119px;" type="file" class="btn btn-default" id="pancopy" name="file" onchange="return ValidPanRegUpload()" value="Upload PAN" required="required">
        <div id="errorBoxImgPan"></div>
        <div class="col-md-5">
            <img class="img-responsive" id="image2_preview">
        </div>
        <div class="col-md-5" id="show_pan_button" style="display:none">
            <input style="margin-top: 9px; margin-left: 119px;" class="btn btn-primary" type="submit" value="Upload" name="pancopy_name" id="pancopy_submit" />
            <div id="errorBoxSubmitPan"></div>
        </div>
    </div>
</form>
<input type="submit" id="step-3" name="step-3" onclick="return saveBank();" class="btn btn-primary col-md-2 col-md-offset-5" value="Save">
<script>
    function saveBank() {
         if ($.trim($("#pancopy").val()) == '') { //there should be only if
            $("#pancopy").focus();
            $("#errorBoxImgPan").removeClass('hide');
            $("#errorBoxImgPan").html("Please upload your PAN copy");
            return false;
        } else if ($("pancopy_submit").value != "") {
            $("#pancopy_submit").focus();
            $("#errorBoxSubmitPan").removeClass('hide');
            $("#errorBoxSubmitPan").html("Please click the Upload button to upload your PAN copy");
            return false;
        } else if ($.trim($("#copyvat").val()) == '') {
            $("#copyvat").focus();
            $("#errorBoxImgVat").removeClass('hide');
            $("#errorBoxImgVat").html("Please upload your VAT copy");
            return false;
        } else if ($("vat_submitcopy").value != "") {
            $("#vat_submitcopy").focus();
            $("#errorBoxVatSubmit").removeClass('hide');
            $("#errorBoxVatSubmit").html("Please click the Upload button to upload your VAT copy");
            return false;
        }
        $.ajax({
            url: "seller_bank_save.php",
            type: "POST",
            data: postData,
            success: function(data) {
                alert(data);
                /*$("#bank_name").val('');
                $('#branch_name').val('');
                $('#holder_name').val('');
                $("#account_no").val('');
                $("#typeacc").val('');
                $("#branchcode").val('');
                $("#panno").val('');
                $("#code_ifsc").val('');*/
                $('#new_show').hide();
                $('#new_store').hide();
                $('#new_bank').hide();
                $('#new_product').show();
                $('#new2').removeClass('disabled');
                $('#new3').removeClass('disabled');
                $('#new4').removeClass('disabled');
                $('#new2').addClass('active');
                $('#new3').addClass('active');
                $('#new4').addClass('active');
                goToProduct();
            }
        });
        return false;
    }
</script>

好的，但上传按钮应该只在预览图像后进行一次验证