フォームの入力値をobjectとして取得するよ

util.form.data.js

/**
 * フォーム内の入力値をobjectとして取得する
 *
 * @param {Node} form
 * @return {Object}
 */
function getFormData(form) {
  if (form.tagName !== 'FORM') {
    throw new TypeError('Argument must be HTMLFormElement.');
  }

  var elms = toArray(form.elements),
    e, i, pos, isAry, name, val, rv = {},
    list = [], li,
    option, j, jz;

  // form.elementsに，INPUT[type="image"]要素は含まれない
  if (form.innerHTML.indexOf('type="image"') || form.innerHTML.indexOf("type='image'")) {
    list = toArray(form.getElementsByTagName('input'));
    i = 0;
    while (li = list[i++]) {
      if (li.type === 'image') {
        elms.push(li);
      }
    }
  }

  i = 0;
  while (e = elms[i++]) {
    // form.elementsに，FIELDSET要素も含まれる
    if (
      e.disabled === true ||
      e.type === 'radio'    && e.checked === false ||
      e.type === 'checkbox' && e.checked === false ||
      e.tagName === 'FIELDSET' ||
      0
    ) {
      continue;
    }

    pos   = e.name.indexOf('[');
    isAry = pos !== -1;
    name  = isAry ? e.name.substr(0, pos) : e.name;
    val   = e.value;
    
    // multiple属性のついたSELECT要素
    if (e.tagName === 'SELECT' && e.multiple === true && isAry) {
      rv[name] || (rv[name] = []);

      j   = 0;
      jz  = e.length;
      for (; j<jz; j++) {
        option = e[j];
        if (option.selected === true) {
          rv[name].push(option.value);
        }
      }
    } else if (isAry) {
      rv[name] || (rv[name] = []);

      rv[name].push(val);
    } else {
      rv[name] = val;
    }
  }

  return rv;
}