with all this hype surrounding promisifying callbacks, i thought i would spice things up, and offer a function that callbackifies promises.

callbackify.js

function callbackify (promise) {
  return function execute() {
    const callback = arguments[arguments.length - 1];
    const args = Array.prototype.slice.call(arguments, 0, arguments.length - 1);
    if (promise instanceof Promise) promise.then(r => callback(null, r)).catch(callback);
    else if (typeof promise === 'function') promise(...args).then(r => callback(null, r)).catch(callback);
    else throw new TypeError('`promise` must be a Promise or Function which returns a Promise!');
  }
}