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.