Promise wrapper - turns any async function with callback into a ES6 Promise

callback-promise.js

let promise = ( func, ...args ) => {

  return new Promise( ( resolve, reject ) => {
    let callback = ( error, data ) => {
      if (error) reject(error);
      else resolve(data);
    };
    args.push(callback);
    func.apply(func, args);
  });

};