express-promise-router
v4.1.1
Published
A lightweight wrapper for Express 4's Router that allows middleware to return promises
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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
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
.
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();
});
ES6 Imports
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();
Async / Await
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}!`);
})
Error handling
Just like with regular express.Router
you can define custom error handlers.
router.use((err, req, res, next) => {
res.status(403).send(err.message);
});
Frequently Asked Questions
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.
Can i use this on 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");
});
Why aren't promise values sent to the client
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.
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
See CHANGELOG
Attribution
Licensed under the MIT license.
Initial implementation by Alex Whitney
Maintained by Moritz Mahringer
Contributed to by awesome people