Bootstrap Modal before form Submit

So if I get it right, on click of a button, you want to open up a modal that lists the values entered by the users followed by submitting it.

For this, you first change your input type="submit" to input type="button" and add data-toggle="modal" data-target="#confirm-submit" so that the modal gets triggered when you click on it:

<input type="button" name="btn" value="Submit" id="submitBtn" data-toggle="modal" data-target="#confirm-submit" class="btn btn-default" />

Next, the modal dialog:

<div class="modal fade" id="confirm-submit" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
    <div class="modal-dialog">
        <div class="modal-content">
            <div class="modal-header">
                Confirm Submit
            </div>
            <div class="modal-body">
                Are you sure you want to submit the following details?

                <!-- We display the details entered by the user here -->
                <table class="table">
                    <tr>
                        <th>Last Name</th>
                        <td id="lname"></td>
                    </tr>
                    <tr>
                        <th>First Name</th>
                        <td id="fname"></td>
                    </tr>
                </table>

            </div>

            <div class="modal-footer">
                <button type="button" class="btn btn-default" data-dismiss="modal">Cancel</button>
                <a href="#" id="submit" class="btn btn-success success">Submit</a>
            </div>
        </div>
    </div>
</div>

Lastly, a little bit of jQuery:

$('#submitBtn').click(function() {
     /* when the button in the form, display the entered values in the modal */
     $('#lname').text($('#lastname').val());
     $('#fname').text($('#firstname').val());
});

$('#submit').click(function(){
     /* when the submit button in the modal is clicked, submit the form */
    alert('submitting');
    $('#formfield').submit();
});

You haven't specified what the function validateForm() does, but based on this you should restrict your form from being submitted. Or you can run that function on the form's button #submitBtn click and then load the modal after the validations have been checked.

DEMO

You can use browser default prompt window. Instead of basic <input type="submit" (...) > try:

<button onClick="if(confirm(\'are you sure ?\')){ this.form.submit() }">Save</button>