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express-promise-router
Advanced tools
A lightweight wrapper for Express 4's Router that allows middleware to return promises
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.
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'));
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 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 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.
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.
Install the module with npm
npm install express-promise-router --save
or yarn.
yarn add express-promise-router
express-promise-router
is a drop-in replacement for Express 4's Router
.
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();
});
express-promise-router
can be imported via ES6 imports. The Router
constructor is the default export.
import Router from "express-promise-router";
const router = Router();
Using async
/ await
can dramatically improve code readability.
router.get('/url', async (req, res) {
const user = await User.fetch(req.user.id);
if (user.permission !== "ADMIN") {
throw new Error("You must be an admin to view this page.");
}
res.send(`Hi ${user.name}!`);
})
Just like with regular express.Router
you can define custom error handlers.
router.use((err, req, res, next) => {
res.status(403).send(err.message);
});
Cannot read property '0' of undefined
This error may indicate that you call a method that needs a path, without one.
Calling router.get
(or post
, all
or any other verb) without a path is not
valid. You should always specify a path like this:
// DO:
router.get("/", function (req, res) {
res.send("Test");
});
// DON'T:
router.get(function (req, res) {
res.send("Test");
});
For more information take a look at this comment.
app
?We currently don't support promisifying the app
object. To use promises with
the top-level router we recommend mounting a Router
on the app object, like
this:
import express from "express";
import Router from "express-promise-router";
const app = express();
const router = Router();
app.use(router);
router.get("/", function (req, res) {
res.send("Test");
});
We don't send values at the end of the promise chain to the client, because this
could easily lead to the unintended leak of secrets or internal state. If you
intend to send the result of your chain as JSON, please add an explicit
.then(data => res.send(data))
to the end of your chain or send it in the last
promise handler.
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
.
See CHANGELOG
Licensed under the MIT license.
Initial implementation by Alex Whitney
Maintained by Moritz Mahringer
Contributed to by awesome people
4.1.1
FAQs
A lightweight wrapper for Express 4's Router that allows middleware to return promises
The npm package express-promise-router receives a total of 171,597 weekly downloads. As such, express-promise-router popularity was classified as popular.
We found that express-promise-router demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 2 open source maintainers collaborating on the project.
Did you know?
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