Convert callback-based javascript to ES6 Promises
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Latest commit 7fc27d7 Oct 20, 2018

Travis CI


Converts callback-based functions to ES6/ES2015 Promises, using a boilerplate callback function.

NOTE: All-new API for Version 6.0.0; please read carefully!


Install with npm

npm install es6-promisify


const {promisify} = require("es6-promisify");

// Convert the stat function
const fs = require("fs");
const stat = promisify(fs.stat);

// Now usable as a promise!
stat("example.txt").then(function (stats) {
    console.log("Got stats", stats);
}).catch(function (err) {
    console.error("Yikes!", err);

Promisify methods

const {promisify} = require("es6-promisify");

// Create a promise-based version of send_command
const redis = require("redis").createClient(6379, "localhost");
const client = promisify(redis.send_command.bind(redis));

// Send commands to redis and get a promise back
client("ping").then(function (pong) {
    console.log("Got", pong);
}).catch(function (err) {
    console.error("Unexpected error", err);
}).then(function () {

Handle multiple callback arguments, with named parameters

const {promisify} = require("es6-promisify");

function test(cb) {
    return cb(undefined, 1, 2, 3);

// Create promise-based version of test
test[promisify.argumentNames] = ["one", "two", "three"];
const multi = promisify(test);

// Returns named arguments
multi().then(result => {
    console.log(result); // {one: 1, two: 2, three: 3}

Provide your own Promise implementation

const {promisify} = require("es6-promisify");

// Now uses Bluebird
promisify.Promise = require("bluebird");

const test = promisify(cb => cb(undefined, "test"));
test().then(result => {
    console.log(result); // "test", resolved using Bluebird


Test with tape

$ npm test

Changes from v5.0.0

  • Allow developer to specify a different implementations of Promise
  • No longer ships with a polyfill for Promise. If your environment has no native Promise you must polyfill yourself, or set promisify.Promise to an A+ compatible Promise implementation.
  • Removed support for settings.thisArg: use .bind() instead.
  • Removed support for settings.multiArgs: use named arguments instead.

Published under the MIT License.