serialize form field into json object

jquery.serializeobject.js

$.fn.serializeObject = function() {
    var o = {};
    var a = this.serializeArray();
    $.each(a, function() {
        if (o[this.name]) {
            if (!o[this.name].push) {
                o[this.name] = [o[this.name]];
            }
            o[this.name].push(this.value || '');
        } else {
            o[this.name] = this.value || '';
        }
    });
    return o;
};

var data = $("form").serializeObject();
// and then, i'll add some extra param
data["extra"] = "hello world";
$.ajax({
    data: data,
    ....
});