@google-cloud/promisify

What is @google-cloud/promisify?

@google-cloud/promisify is a utility library that helps convert callback-based functions to promise-based functions. This is particularly useful for modern JavaScript development where promises and async/await syntax are preferred over traditional callback patterns.

What are @google-cloud/promisify's main functionalities?

Promisify a single function

This feature allows you to convert a single callback-based function to a promise-based function. The code sample demonstrates how to use the `promisify` function to convert a traditional callback function into one that returns a promise.

const {promisify} = require('@google-cloud/promisify');

function callbackFunction(arg1, arg2, callback) {
  // Simulate an asynchronous operation
  setTimeout(() => {
    callback(null, 'result');
  }, 1000);
}

const promiseFunction = promisify(callbackFunction);

promiseFunction('arg1', 'arg2').then(result => {
  console.log(result); // 'result'
}).catch(err => {
  console.error(err);
});

Promisify all functions in an object

This feature allows you to promisify all functions in an object. The code sample demonstrates how to use the `promisifyAll` function to convert all callback-based functions in an object to promise-based functions, appending 'Async' to the function names.

const {promisifyAll} = require('@google-cloud/promisify');

const obj = {
  callbackFunction(arg1, arg2, callback) {
    setTimeout(() => {
      callback(null, 'result');
    }, 1000);
  }
};

promisifyAll(obj);

obj.callbackFunctionAsync('arg1', 'arg2').then(result => {
  console.log(result); // 'result'
}).catch(err => {
  console.error(err);
});

Other packages similar to @google-cloud/promisify

util.promisify

The `util.promisify` function is a built-in Node.js utility that converts callback-based functions to promise-based functions. It is similar to @google-cloud/promisify but is part of the Node.js standard library, making it a more straightforward choice for many developers.

bluebird

Bluebird is a fully-featured promise library that includes a `promisify` function to convert callback-based functions to promise-based ones. It offers more features and better performance compared to @google-cloud/promisify, but it is a larger library and may be overkill for simple use cases.

pify

Pify is a lightweight library that provides a simple way to promisify callback-based functions. It is similar to @google-cloud/promisify but is more minimalistic and has fewer dependencies, making it a good choice for smaller projects.

README

Google Cloud Common Promisify: Node.js Client

A simple utility for promisifying functions and classes.

• Google Cloud Common Promisify Node.js Client API Reference

• github.com/googleapis/nodejs-promisify

Read more about the client libraries for Cloud APIs, including the older Google APIs Client Libraries, in Client Libraries Explained.

Table of contents:

• Quickstart

  • Installing the client library
  • Using the client library

• Samples

• Versioning

• Contributing

• License

Quickstart

Installing the client library

npm install @google-cloud/promisify

Using the client library

const {promisify} = require('@google-cloud/promisify');

/**
 * This is a very basic example function that accepts a callback.
 */
function someCallbackFunction(name, callback) {
  if (!name) {
    callback(new Error('Name is required!'));
  } else {
    callback(null, `Well hello there, ${name}!`);
  }
}

// let's promisify it!
const somePromiseFunction = promisify(someCallbackFunction);

async function quickstart() {
  // now we can just `await` the function to use it like a promisified method
  const [result] = await somePromiseFunction('nodestronaut');
  console.log(result);
}
quickstart();

It's unlikely you will need to install this package directly, as it will be installed as a dependency when you install other @google-cloud packages.

Samples

Samples are in the samples/ directory. The samples' README.md has instructions for running the samples.

Sample	Source Code	Try it
Quickstart	source code

The Google Cloud Common Promisify Node.js Client API Reference documentation also contains samples.

Versioning

This library follows Semantic Versioning.

This library is considered to be General Availability (GA). This means it is stable; the code surface will not change in backwards-incompatible ways unless absolutely necessary (e.g. because of critical security issues) or with an extensive deprecation period. Issues and requests against GA libraries are addressed with the highest priority.

More Information: Google Cloud Platform Launch Stages

Contributing

Contributions welcome! See the Contributing Guide.

License

Apache Version 2.0

See LICENSE

Changelog

1.0.1 (2019-06-14)

Bug Fixes

• docs: move to new client docs URL (#124) (34d18cd)