express-promise-router

What is express-promise-router?

express-promise-router is an npm package that provides a drop-in replacement for Express's Router, adding support for handling promises. This allows you to write route handlers that return promises and automatically handle errors, making your code cleaner and more readable.

What are express-promise-router's main functionalities?

Promise-based Route Handling

This feature allows you to define routes that return promises. The router will automatically catch any errors and pass them to the next middleware.

const express = require('express');
const router = require('express-promise-router')();

router.get('/example', async (req, res) => {
  const data = await someAsyncFunction();
  res.json(data);
});

const app = express();
app.use(router);
app.listen(3000, () => console.log('Server running on port 3000'));

Error Handling

This feature demonstrates how express-promise-router handles errors thrown in async route handlers. The error is automatically caught and passed to the error-handling middleware.

const express = require('express');
const router = require('express-promise-router')();

router.get('/error', async (req, res) => {
  throw new Error('Something went wrong');
});

const app = express();
app.use(router);
app.use((err, req, res, next) => {
  res.status(500).json({ error: err.message });
});
app.listen(3000, () => console.log('Server running on port 3000'));

Middleware Support

This feature shows how you can use async middleware with express-promise-router. The middleware can perform asynchronous operations and call next() to proceed to the next middleware or route handler.

const express = require('express');
const router = require('express-promise-router')();

const asyncMiddleware = async (req, res, next) => {
  await someAsyncFunction();
  next();
};

router.use(asyncMiddleware);
router.get('/middleware', (req, res) => {
  res.send('Middleware executed');
});

const app = express();
app.use(router);
app.listen(3000, () => console.log('Server running on port 3000'));

Other packages similar to express-promise-router

express-async-handler

express-async-handler is a middleware for handling exceptions inside of async express routes and passing them to your express error handlers. Unlike express-promise-router, it is not a router replacement but a middleware that you wrap around your async route handlers.

async-express-router

async-express-router is another package that provides a router with built-in support for async route handlers. It is similar to express-promise-router but offers additional features like route grouping and middleware chaining.

express-async-router

express-async-router is a lightweight alternative to express-promise-router that also supports async route handlers. It focuses on simplicity and minimalism, providing a straightforward way to handle promises in Express routes.

README

express-promise-router

A simple wrapper for Express 4's Router that allows middleware to return promises. This package makes it simpler to write route handlers for Express when dealing with promises by reducing duplicate code.

Getting Started

Install the module with: npm install express-promise-router --save.

express-promise-router is a drop-in replacement for Express 4's Router.

Documentation

Middleware and route handlers can simply return a promise. If the promise is rejected, express-promise-router will call next with the reason. This functionality removes the need to explicitly define a rejection handler.

// With Express 4's router
var router = require('express').Router();

router.use('/url', function (req, res, next) {
    Promise.reject().catch(next);
})

// With express-promise-router
var router = require('express-promise-router')();

router.use('/url', function (req, res) {
    return Promise.reject();
})

Calling next() and next('route') is supported by resolving a promise with either 'next' or 'route'. No action is taken if the promise is resolved with any other value.

router.use('/url', function (req, res) {
    // equivalent to calling next()
    return Promise.resolve('next');
});

router.use('/url', function (req, res) {
    // equivalent to calling next('route')
    return Promise.resolve('route');
});

This package still allows calling next directly.

router = require('express-promise-router')();

// still works as expected
router.use('/url', function (req, res, next) {
    next();
});

Contributing

Add unit tests for any new or changed functionality. Lint and test your code using npm test.

Unit tests use mocha and chai.

We use eslint, but styling is controlled mostly by prettier which reformats your code before you commit. You can manually trigger a reformat using npm run-script format.

Release History

v3.0.0

• Update to chai 4
• Update to mocha 4
• Update to eslint 4
• Update to sinon 4
• Reduced lodash usage and footprint #41
• Added TypeScript definitions #47

v2.0.0

• Dropped support for old Node versions (<4).
  • Supported: Node 4 LTS, Node 6 LTS, Node current.
• Use native promises instead of bluebird. (One less dependency!)
• Use is-promise module instead of our own function.

v1.1.1

• Update to lodash 4
• Update to bluebird 3

v1.1.0

• Improvements to error reporting
• Support for route array
• Bug fixes

License

Copyright (c) 2014 Alex Whitney. Licensed under the MIT license.

Changelog

v3.0.0

• Update to chai 4
• Update to mocha 4
• Update to eslint 4
• Update to sinon 4
• Reduced lodash usage and footprint #41
• Added TypeScript definitions #47