Serialize form inputs into JSON, with support for `name[]` syntax.

jquery.serialize-json.js

(function($) {
  $.extend($.fn, {
    serializeJson: function() {
      var payload = {},
          regex = /^(\w+)\[(\d*)\]$/;

      $.each($(this).serializeArray(), function(i, input) {
        var res = input.name.match(regex);
          if(res) {
            if(! (res[1] in payload)) {
              payload[res[1]] = [];
            }

            var array = payload[res[1]];

            if(res[2] == '') {
              array[array.length] = input.value;
            } else {
              // Ensure that the value gets inserted at exactly
              //  the right spot.
              while(array.length < res[2]) {
                array[array.length] = null;
              }

              array.splice(res[2], 0, input.value);
            }
          } else {
            payload[input.name] = input.value;
          }
      });

      return JSON.stringify(payload);
    }
  });
})(jQuery);