code: function _parseKey(key) {
    const result = key.match(/^(.+)\[([0-9]+)\]$/);
  
    if (result) {
      return {element: result[1], index: parseInt(result[2], 10)};
    } else {
      return {element: key, index: null};
    }
  }
docs: 'builds[0]' -> { element: builds, index: 0 } 'builds' -> { element: builds, index: null }