es6-promisify

What is es6-promisify?

The es6-promisify package is a utility that converts callback-based functions to return Promises, making it easier to work with asynchronous code in a more modern and readable way.

What are es6-promisify's main functionalities?

Promisify a single callback-based function

This feature allows you to convert a single callback-based function, such as `fs.readFile`, into a function that returns a Promise. This makes it easier to handle asynchronous operations using modern async/await syntax or Promise chaining.

const promisify = require('es6-promisify');
const fs = require('fs');
const readFileAsync = promisify(fs.readFile);

readFileAsync('example.txt', 'utf8')
  .then(data => console.log(data))
  .catch(err => console.error(err));

Promisify an entire object of callback-based functions

This feature allows you to promisify all functions within an object, such as the `fs` module, so that all of its methods return Promises. This is useful for working with modules that have multiple callback-based methods.

const promisify = require('es6-promisify');
const fs = require('fs');
const fsAsync = promisify(fs);

fsAsync.readFile('example.txt', 'utf8')
  .then(data => console.log(data))
  .catch(err => console.error(err));

Other packages similar to es6-promisify

util.promisify

The `util.promisify` function is a built-in Node.js utility that provides similar functionality to es6-promisify. It converts callback-based functions to return Promises. Since it is built into Node.js, it does not require an additional package installation. However, it is only available in Node.js versions 8.0.0 and above.

bluebird

Bluebird is a fully-featured Promise library that includes a `promisify` method. It offers more advanced features and better performance compared to es6-promisify. Bluebird is a good choice if you need additional Promise utilities and optimizations.

pify

Pify is a lightweight utility that promisifies callback-style functions. It is similar to es6-promisify but offers more customization options, such as filtering which methods to promisify and handling multiple arguments. Pify is a good alternative if you need more control over the promisification process.

README

es6-promisify

Converts callback-based functions to Promise-based functions.

Install

Install with npm

npm install --save es6-promisify

Example

"use strict";

// Declare variables
var promisify = require("es6-promisify"),
    fs = require("fs"),

// Convert the stat function
    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);
});

Provide your own callback

"use strict";

// Declare variables
var promisify = require("es6-promisify"),
    fs = require("fs"),
    stat;

// Convert the stat function, with a custom callback
stat = promisify(fs.stat, function (err, result) {
    if (err) {
        console.error(err);
        return this.reject("Could not stat file");
    }
    this.resolve(result);
});

stat("example.txt").then(function (stats) {
    console.log("Got stats", stats);
}).catch(function (err) {
    // err = "Could not stat file"
});

Promisify methods

"use strict";

// Declare variables
var promisify = require("es6-promisify"),
    redis = require("redis").createClient(6379, "localhost"),

// Create a promise-based version of send_command
    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 () {
    redis.quit();
});

Tests

Test with nodeunit

$ npm test

Published under the MIT License.