$.serializeJSON()

gistfile1.js

// Rails-style JSON serialization. e.g., Given a form:
//
//   <input type="text" name="foo[bar][]" value="qux" />
//   <input type="text" name="foo[bar][]" value="quux" />
//
// $("form").serializeJSON() will serialize to
//
//    { foo: { bar: [ "qux", "quux" ] } }
//
$.fn.serializeJSON = function() {
  var json = {},
      tokenize = function(input) {
        return input.split('[')
          .map(function(t) {
            return t.replace(']', '');
          });
      },
      baseObject = function(json, tokens, depth) {
        var out = json;
        for (var i = 0; i < depth; i++)
          out = out[tokens[i]];

        return out;
      };

  jQuery.map($(this).serializeArray(), function(n, i) {
    var name   = n['name'],
        tokens = tokenize(name),
        value  = n['value'];

    for (var i = tokens.length - 1; i > -1; i--) {
      var token = tokens[i], tmp = {};

      // If the token is blank, we're dealing with an array.
      // Handle this by wrapping the single value in an array
      // and attaching it to the next token up if it's an array,
      // or just creating a new array if not.
      //
      if (token == "") {
        if ((base = baseObject(json, tokens, i)) && $.isArray(base)) {
          base.push(value);
          i = 0; // We've updated the final output, so just break out of loop
        } else {
          tmp = [value];
        }
      } else {
        tmp[token] = value;
      }
      value = tmp;
    }
    $.extend(true, json, value);
  });
  return json;
};