Best attempt at a general wrapper around many types of callbacks.

promisify.js

/**
 * Wraps the given callback in a promise
 * @param {function} callback - Callback to call & wrap in a promise
 * @param {...*} args - Arguments to send to the callback. Send the promise
 *                      method to prefil arguments.
 * @returns {promise} A promise resolved when callback is fired
 * @example
 * return promise(this.setState, data);
 * return promise(setTimeout, promise, 500);
 */
export default function promise (callback, ...args) {
  return new Promise((resolve, reject) => {
    let index = args.indexOf(promise);

    function handler (...results) {
      let err = results[0];

      if (err && err instanceof Error) reject(err);
      else resolve(results);
    }

    /** Add the handler at the given promise arg or at the end */
    args.splice(index > -1 ? index : args.length, 1, handler);

    callback(...args);
  });
}