promisifyAll implemented with util.promisify

  • pifall

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pifall is an implementation of promisifyAll in terms of Node 8's included util.promisify.
That is, it will iterate over your object's properties (Reflect.ownKeys), and make an Async-suffixed copy of any functions it finds. If it runs into a getter, it will create the Async version, which will grab the value from the getter, and work as normal, if the value ends up being a function. Otherwise it will throw.
The Async-suffixed versions are as returned by util.promisify.
In the event that you already have a foo and a fooAsync, the fooAsync will be overwritten. If it's not writable, or not configurable, pifall will make no attempt to circumvent that, meaning it will throw.
Note that pifall operates in-place on the object. It does not return anything, and the original object is augmented with the new methods.
pifall will flat-out refuse to promisify a built-in prototype, even it it's in a prototype chain when the proto option is provided. It will also flat-out refuse to promisify objects whose typeof is not function or object. It will do this by throwing a TypeError.
On versions of Node not supporting util.promisify, a polyfill is used.


const obj = {
  func (cb) {
    setImmediate(() => {
      cb(null, 'hello');


obj.funcAsync().then(result => console.assert(result === 'hello'));

It can also take a second parameter, an optional options object, with the following properties:
  • proto: If truthy, this causes pifall to include any properties
accessible on the object, including those in its prototype chain. Default is false;
  • classes: If truthy, this causes pifall to treat functions whose names
start with a capital letter as "classes". That is, the function itself will not be promisified, but its prototype will be pifalled. (Note: This does not currently work for functions retrieved via getters. No matter what, these are treated as ordinary non-class functions. In practice, this doesn't come up a whole lot.) Default is false.
  • suffix: Sets the suffix for promisified versions of functions. Default
is 'Async'.
  • promisifier: Use custom promisifier instead of util.promisify


MIT License. See LICENSE.txt.