Overview
Express.js, commonly referred to simply as Express, is a popular web application framework for Node.js designed to build websites, web applications, and APIs. One common task when working with Express is retrieving the full URL of a request. This can be important for logging, authentication, redirects, and more. Retrieving the full URL is simple but essential, and understanding how to do it can be invaluable in many scenarios.
In this article, we’ll look at several ways to retrieve the full URL in an Express.js application. We will begin with basic methods and gradually move to more advanced techniques to handle various use cases.
Basic Example: Using req.protocol, req.get(‘host’), and req.originalUrl
const express = require('express');
const app = express();
app.get('*', (req, res) => {
const fullUrl = `
<code>${req.protocol}://${req.get('host')}${req.originalUrl}</code>`;
res.send(`Full URL: ${fullUrl}`);
});
app.listen(3000, () => {
console.log('Server is running on port 3000');
});
This basic example demonstrates how to concatenate the protocol, host, and original URL to form the full URL within a wildcard GET route.
Using req.href in Middleware
app.use((req, res, next) => {
req.fullUrl = `${req.protocol}://${req.get('host')}${req.originalUrl}`;
next();
});
app.get('/example', (req, res) => {
res.send('Full URL retrieved in middleware: ' + req.fullUrl);
});
Using middleware allows us to attach the full URL to the request object, making it available to all subsequent route handlers.
Advanced Example: Considering Proxies and Load Balancers
When behind a proxy or load balancer, such as Nginx, the req.protocol and req.get(‘host’) may not give the accurate result due to the client’s request being forwarded. Therefore, we need to trust the ‘X-Forwarded-*’ headers.
app.enable('trust proxy');
app.use((req, res, next) => {
req.fullUrl = `${req.protocol}://${req.get('host')}${req.originalUrl}`;
next();
});
By enabling ‘trust proxy’, Express knows to trust the headers set by the proxy for the original request information.
Generating Full URLs for API Responses
Sometimes, API endpoints need to return full URL references in their responses. Here’s a method to generate URLs dynamically:
app.get('/api/data', (req, res) => {
const data = {
userId: 1,
resourceUrl: `${req.protocol}://${req.get('host')}/api/users/1`
};
res.json(data);
});
This practice is common for providing navigable links in API responses, often known as HATEOAS (Hypermedia as the Engine of Application State).
Conclusion
Understanding how to retrieve the full URL in an Express application is a small but crucial part of backend development. It’s a tool that’s useful in a variety of situations from debugging to creating reliable API services. Throughout this tutorial, we explored the basic, middleware-based, and proxy-aware methods for getting the full URL, along with making your API responses more dynamic and user-friendly with full URL paths. Apply these techniques as appropriate in your applications to enhance their functionality and reliability.
