code: function getCustomProperties(object) {
    var result = {};
    for (var key in object) {
      if (/^x-/.test(key)) {
        result[key] = object[key];
      }
    }
    return result;
  }
docs: /*
  Filter object on keys matching the prefix `x-`.
  @param object {object} - object to fetch properties from
  @returns {object} - object with only properties prefixed with `x-`