promisify

Simple, standalone promisification

This is a straightforward, no-frills implementation that will work on any asynchronous functions that take node-style callbacks.

You can always use the promisify that comes with Bluebird, but sometimes you may want to keep things native.

Install

npm install @jaawerth/promisify

Usage

var promisify = require('@jaawerth/promisify');
promisify(asyncCallbackFn[, thisArg]);

Use the global Promise constructor, the included shim, OR bring your own

Global Promise object (default)

const promisify = require('@jaawerth/promisify');
const readFile = promisify(require('fs').readFile);

readFile('./foo.txt', 'utf8').then(console.log);

Custom Promise constructor

Just make sure your Promise implementation adheres to the Promise constructor's API and behavior, and you can instantiate a promisify that will use it.

promisify = promisify.create(MyPromise);

Shim (uses es6-promise)

var promisify = require('@jaawerth/promisify/shim');

Keep the promisified function bound to its context as needed

var crabWalk = promisify(zoidberg.crabWalk, zoidberg);
crabWalk().then(runAway);

Or don't!

Just like any unbound function, you can manipulate context at will.

var promiseMe = promisify(function returnMe() {
  return this;
});

promiseMe.call('No!'); // => Resolves to 'No!'