Pure _.get from lodash

_.get.js

function _stringToPath(path) {
  const containsBracketNotation = /\[[0-9]+\]/g;
  if (path.match(containsBracketNotation)) {
    path = path.replace(containsBracketNotation, s => `.${s.substring(1, s.length - 1)}`);
  }
  return path.split('.');
}

function get(source, path, defaultArgument) {
  return _stringToPath(path).reduce((nestedObject, key) => {
    return nestedObject && key in nestedObject ? nestedObject[key] : void 0;
  }, source) || defaultArgument;
}