Не уверен, хотите ли вы jQuery.
var form;
form.onsubmit = function (e) {
// stop the regular form submission
e.preventDefault();
// collect the form data while iterating over the inputs
var data = {};
for (var i = 0, ii = form.length; i < ii; ++i) {
var input = form[i];
if (input.name) {
data[input.name] = input.value;
}
}
// construct an HTTP request
var xhr = new XMLHttpRequest();
xhr.open(form.method, form.action, true);
xhr.setRequestHeader('Content-Type', 'application/json; charset=UTF-8');
// send the collected data as JSON
xhr.send(JSON.stringify(data));
xhr.onloadend = function () {
// done
};
};