ES6 Generators support for expressjs

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1.1.26 years ago8 years agoMinified + gzip package size for express-yields in KB


ExpressJS Yields
A dead simple ES6 generators and ES7 async/await support hack for ExpressJS


npm install express-yields --save

Then require this script somewhere before you start using it:
const express = require('express');
const yields = require('express-yields');
const User = require('./models/user');
const app = express();

app.get('/users', function* (req, res) {
  const users = yield User.findAll(); // <- some Promise

// or with node 7 async/await
app.get('/users', async (req, res) => {
  const users = await User.findAll(); // <- some Promise

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 a generator function, you don't need to do that. If you want to pass an error, just throw a normal exception:
app.use(function * (req, res) {
  const user = yield User.findByToken(req.get('authorization'));

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

// the same with Node 7 async/await
app.use(async (req, res) => {
  const user = await User.findByToken(req.get('authorization'));

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

How Does This Work?

This is a 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.

Copyright & License

All code in this repository released under the terms of the ISC license.
Copyright (C) 2016 Nikolay Nemshilov