jQuery transparent submission plugin - uses iFrames to allow for an 'ajax-like' submission of a form to some endpoint, and retrieve the json, html or text response offered by that server to said frame.

jquery.transparentsubmit.js

/**
 * jQuery plugin for transparent submission of a form using an $.ajax-like interface.
 * Usage Examples:
 * $.transparentSubmit({dataType:'json', form:$('#myForm')})
 * $('#myForm').transparentSubmit({dataType:'html'})
 * Supports Deferred (.done, .fail, .when, etc.)
 */
(function($){
    $.transparentSubmit = function(options){
        var defer = $.Deferred(), // Deferred object whose promise we will hook into when adding .done, etc to calls
            options = $.extend({
                dataType:'json'
            }, (options || {})), // coerce options into being an object, extend defaults
            name = 'target-'+Math.random().toString(36).substring(7), // assign a psuedo-random name to the frame
            hiframe = $('<iframe id="'+name+'" name="'+name+'" src="about:blank" ' +
                'style="width:0;height:0;border:0px solid #fff;"></iframe>'), // create invisible iframe - NOT display:none
            form = $(options.form), // get form, make sure its a jquery object
            cleanup = function(){
                hiframe.remove();
                delete frames[name];
            }; // clean iframe away when we're finished with it
        if (!form.length || form[0].tagName !== 'FORM'){ // if we don't have a form to submit, reject (call .fail)
            defer.reject("No form element specified to submit.");
            return defer.promise();
        }

        form.attr('target', name).append(hiframe); // set target of form to iframe, and append iframe to the form

        // On load event, grab and parse the contents of the iframe
        hiframe.on('load', function(){
            var res;

            form.removeAttr('target');

            try{
                if (options.dataType.indexOf('json') != -1)
                { // browsers will wrap a json return with <pre></pre>
                    res = frames[name].document.getElementsByTagName("pre")[0].innerHTML;
                }
                else
                {
                    res = frames[name].document.getElementsByTagName('body')[0].innerHTML;
                }
            }catch(e){
                // Failed to receive anything in the body of the frame
                cleanup();
                defer.reject("Failed to receive response in form target "+name+": "+e.message);
                return;
            }

            cleanup();

            if (options.dataType.indexOf('json') != -1)
            {
                try{
                    res = $.parseJSON(res);
                }catch(e){
                    defer.reject("Failed to parse response into JSON: "+e.message);
                    return;
                }
            }
            else if (options.dataType.indexOf('html') != -1)
            {
                res = $.parseHTML(res);
            }

            defer.resolve(res); // Finished (call .done)
        });

        form.submit();

        return defer.promise();
    }

/*
* This allows us the option to call $('#myForm').transparentSubmit - as you can see, its just a slightly different form 
* to the plugin, which calls our transparentSubmit function as defined above.
*/
    $.fn.transparentSubmit = function(options){
        options.form = this;
        return $.transparentSubmit(options);
    };
})(jQuery);