Node.js "promisify" implementations

promisify-node4.js

const promisify = (fn) => {
  return function () {
    const args = Array.from(arguments);
    return new Promise(function (resolve, reject) {
      fn.apply(undefined, args.concat([function (error, data) {
        if (error) return reject(error);
        if (data === undefined) return resolve();
        return resolve(data);
      }]));
    });
  };
};

promisify-node6.js

const promisify = (fn) => {
  return (...args) => {
    return new Promise((resolve, reject) => {
      fn(...args, (error, data) => {
        if (error) return reject(error);
        if (data === undefined) return resolve();
        return resolve(data);
      });
    });
  };
};