Migrating Bluebird promises to native ones

We have used bluebird because it was one of the best libraries for promises. But then promises have gained support in both nodejs and browser. That was the easy catch so we decided to remove it from our code base.

The functions we were using of that library were

• BlueBirdPromise.promisify
• BlueBirdPromise.delay

Promisify

Node.js ships with util api which provides same requirement as that of bluebird.

The method works by taking in the common error-first callback-style functions and returns a promises.

1// Before
2
3import Promise from "bluebird";
4const readFile = Promise.promisify(fs.readFile);
5
6// After
7
8import util from "util";
9const readFile = util.promisify(fs.readFile);

Delay

Purpose of this method is to returns a promise that will be resolved after given milliseconds. Native way to do this was to promisify setTimeout function.

1// Before
2
3import Promise from "bluebird";
4await Promise.delay(1000);
5
6// After
7
8import util from "util";
9const setTimeoutAsync = util.promisify(setTimeout);
10await setTimeoutAsync(null, 1000);