ProForm Ajax Example Template -- see http://www.manula.com/manuals/rawaysmith/proform/1.65/en/topic/sample-full-form-template

ajax_form.html

<script type="text/javascript" >
// So the JS knows where our files are
var site_url = "{site_url}";
</script>
{!-- The AJAX code should work with the default HTML generated by the simple form tag: --}
{exp:proform:simple form_name="contact_us"}
<script type="text/javascript" src="http://localhost/index.php//assets/js/contact_us.js"></script>

contact_us.js

$(document).ready(function() {
    ContactUs.init();
});
var ContactUs = {
    $form: undefined,
    $success: undefined,
    init: function() {
        var self = this;
        self.$form = $('#contact_us_proform');
        self.$success = $('.indicator.success');
        self.$success.hide();
        self.bind();
    },
    bind: function() {
        var self = this;
        self.$form.submit(function(e){
            // Stop default submission
            e.preventDefault();
            // Remove any old messages
            self.$form.find('.indicator.error').remove();
            self.$form.find('.indicator.success').hide();
            self.$form.find('li').removeClass('error');
            // Disable the form to prevent double clicks.
            self.$form.find('input[type=submit]').attr('disabled', true);
            // Show an indicator so the user knows something is happening
            self.$form.find('.submit_btn').after('<img src="'+ site_url + 'themes/cp_themes/default/images/indicator.gif" class="spinner" />');
            $.ajax({
                type: "POST",
                url: self.$form.attr('action'),
                data: self.$form.serialize(),
                dataType: "json"
            }).done(function(msg) {
                // Remove it...
                self.$form.find('.spinner').remove();
                if(msg.status == "error") 
                {
                    // Re-enable the form if there are errors
                    self.$form.find('input[type=submit]').attr('disabled', false);
                    for(error in msg.errors) 
                    {
                        switch(error)
                        {
                            case 'email_address' :
                                $('input[email_address]').after('<span class="indicator error">Please enter a valid email</span>').closest('li').addClass('error');
                                break;
                            case 'name' :
                                $('input[name=name]').after('<span class="indicator error">Please enter your name</span>').closest('li').addClass('error');
                                break;
                            case 'captcha' :
                                $('input[name=captcha]').after('<span class="indicator error">Please enter the correct captcha</span>').closest('li').addClass('error');
                                break;
                        }
                    }
                    if($('.form_captcha')) {
                        $('.form_captcha').html(msg.new_captcha);
                    }
                } 
                else if(msg.status == "success") 
                {
                    self.$success.show();
                    self.$form.find('li').removeClass('error');
                }
            });
        });
    }
};