express-async-errors

What is express-async-errors?

The express-async-errors package is a utility for handling errors in asynchronous Express routes and middleware. It allows you to write asynchronous route handlers and middleware without needing to manually catch errors and pass them to the next() function.

What are express-async-errors's main functionalities?

Automatic Error Handling in Async Routes

This feature allows you to write asynchronous route handlers without needing to wrap them in try-catch blocks. Any errors thrown in the async function will be automatically passed to the error-handling middleware.

const express = require('express');
require('express-async-errors');

const app = express();

app.get('/async-route', async (req, res) => {
  // Simulate an async error
  throw new Error('Something went wrong!');
});

app.use((err, req, res, next) => {
  res.status(500).send('Internal Server Error');
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

Automatic Error Handling in Async Middleware

This feature allows you to write asynchronous middleware without needing to wrap them in try-catch blocks. Any errors thrown in the async middleware will be automatically passed to the error-handling middleware.

const express = require('express');
require('express-async-errors');

const app = express();

app.use(async (req, res, next) => {
  // Simulate an async error
  throw new Error('Something went wrong in middleware!');
});

app.get('/', (req, res) => {
  res.send('Hello World');
});

app.use((err, req, res, next) => {
  res.status(500).send('Internal Server Error');
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

Other packages similar to express-async-errors

async-express

The async-express package provides similar functionality by allowing you to use async/await in your Express routes and middleware. It also automatically catches errors and passes them to the next() function. However, it requires you to wrap your routes and middleware with a provided function.

express-promise-router

The express-promise-router package is an alternative to the default Express router that supports async route handlers and middleware. It automatically catches errors and passes them to the next() function. Unlike express-async-errors, it requires you to use a different router object.

README

ExpressJS Async Errors

A dead simple ES6 async/await support hack for ExpressJS

Shamelessly copied from express-yields

This has been lightly reworked to handle async rather than generators.

Usage

npm install express-async-errors --save

Then require this script somewhere before you start using it:

Async functions already work fine in Express.

const express = require('express');
require('express-async-errors');
const User = require('./models/user');
const app = express();

app.get('/users', async (req, res) => {
  const users = await User.findAll();
  res.send(users);
});

This library is about what happens when you hit an error.

A Notice About Calling next

As we all know express sends a function called next into the middleware, which then needs to be called with or without error to make it move the request handling to the next middleware. It still works, but in case of an async function, you don't need to do that. If you want to pass an error, just throw a normal exception:

app.use(async (req, res) => {
  const user = await User.findByToken(req.get('authorization'));

  if (!user) throw Error("access denied");
});

app.use((err, req, res, next) => {
  if (err.message === 'access denied') {
    res.status(403);
    res.json({ error: err.message });
  }

  next(err);
});

How Does This Work?

This is a very minimalistic and unintrusive hack. Instead of patching all methods on an express Router, it wraps the Layer#handle property in one place, leaving all the rest of the express guts intact.

The idea is that you require the patch once and then use the 'express' lib the usual way in the rest of your application.

License

All code in this repository is released under the terms of the ISC license.