Pause form submission for validation

Question

I have some form, which uploads file in an iframe. I'd like to hold it's submission until I'll check if it's valid with ajax. How can I do this ? My code pauses the submission and returns validation result (currently just a dummy function which returns 'result': 'true') but then the 'submit' action is not performed. Also Is it normal that it takes ~2s to show response data after getting response 200 status ?

Here's my html:

<div id="message" style="background:black; width:400px; height:80px; display:none; color:white;">
</div>
<h1>Submit</h1>
<form action="{{upload_url}}" target="upload_target" method="POST" id="file_upload_form" enctype="multipart/form-data">
    {% render_upload_data upload_data %}
    <table>{{ form }}</table>    
    <p>
        <input type="hidden" maxlength="64" name="myfileid" value="{{ myfileid }}" >
    </p>
    <p>
        <input type="submit" id="file_upload_submit" value="Submit" />
    </p>
    <iframe id="upload_target" name="upload_target" src="" style="width:0;height:0;border:0px solid #fff;"></iframe>
</form>

Js:

$(function() {

    $('#file_upload_submit').click(function(e){
        e.preventDefault();
        var fileUploadForm = document.getElementById('file_upload_form');

        $.ajax({
            type: "POST",
            url: '/artifact/upload/check-form/',
            data: 'foo=bar',
            dataType: "json",
            success: function(data){
                if(data['result'] == "true"){
                    $("#message").show();
                    $("#message").fadeIn(400).html('<span>'+data["message"]+'</span>');
                    setTimeout(function(){
                        $("#message").fadeOut("slow", function () {
                            $("#message").hide();
                        });
                    }, 1500);
                     $('#file_upload_form').attr('target','upload_target').submit(function(){
                        alert('Handler for .submit() called.');
                        return false;
                    });
                }
                else{
                    $("#message").show();
                    $("#message").fadeIn(400).html('<span">'+data["message"]+'</span>');
                    setTimeout(function(){
                        $("#message").fadeOut("slow", function () {
                            $("#message").hide();
                        });
                    }, 1500);                    
                    return false;
                }
            }
        });
        return false;        
    });

});    

</script>

and link: http://ntt.vipserv.org/artifact/

---

EDIT

With the code below I'm able to perform validation, then when it's result is positive form is submitted. Now if I hardcode target for form, my alert is not shown and I'm pretty sure that the upload is not performed (unfortunately list of uploads is refreshed each 8h sa I'll know if it worked in some time). If target is not specified, file is uploaded with redirect so the whole 'submit' event listener is ommitted.

<script>  
    $('#fake_upload_submit').click(function(e){
        e.preventDefault();

        var fileUploadForm = document.getElementById('file_upload_form');
        fileUploadForm.addEventListener("submit", function() {
            alert("sent in iframe");
            fileUploadForm.target = 'upload_target';
        }, false);       

        $.ajax({
            type: "POST",
            url: '/artifact/upload/check-form/',
            data: 'foo=bar',
            dataType: "json",
            success: function(data){
                if(data['result'] == "true"){
                    $("#message").show();
                    $("#message").fadeIn(400).html('<span>'+data["message"]+'</span>');
                    setTimeout(function(){
                        $("#message").fadeOut("slow", function () {
                            $("#message").hide();
                        });
                    }, 1500);

                    fileUploadForm.submit();

                }
                else{
                    $("#message").show();
                    $("#message").fadeIn(400).html('<span">Response false</span>');
                    setTimeout(function(){
                        $("#message").fadeOut("slow", function () {
                            $("#message").hide();
                        });
                    }, 1500);                    
                    return false;
                }
            }
        });
        return false;        
    });   
</script>

html:

<div id="message" style="background:black; width:400px; height:80px; display:none; color:white;">
</div>
<h1>Submit</h1>
<form action="{{upload_url}}" method="POST" target="" id="file_upload_form" enctype="multipart/form-data">
    {% render_upload_data upload_data %}
    <table>{{ form }}</table>    
    <p>
        <input type="hidden" maxlength="64" name="myfileid" value="{{ myfileid }}" >
    </p>
    <p>
        <input type="submit" style="display:none" id="true_upload_submit" value="Submit" />
    </p>    
    <iframe id="upload_target" name="upload_target" src="" style="width:0;height:0;border:0px solid #fff;"></iframe>
</form>
    <p>
        <input type="submit" id="fake_upload_submit" value="Submit" />
    </p>

Answer 1

After the validation you register a new submit event handler, but there is nothing that submits the form, so you would have to click the button again to get it submitted.

You can just submit the form instead of adding a submit handler:

$('#file_upload_form').attr('target','upload_target').submit();