support-promise.js

var supportPromise = function (fn) {
  return function () {
    if (typeof arguments[arguments.length - 1] === 'function'
      || typeof Promise === 'undefined') {
      return fn.apply(this, arguments);
    }
    
    var args = arguments;
    
    return new Promise(function (resolve, reject) {
      Array.prototype.push.call(args, function (err, res) {
        err ? reject(err) : resolve(res);
      });
      
      fn.apply(this, args);
    }.bind(this));
  };
};