Express req.baseUrl Property

Posted in Express Tutorial

Updated on Feb 18, 2024

By Mari Selvan

👁️ 40 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

Express.js, a robust web application framework for Node.js, provides various properties and methods to handle HTTP requests effectively.

In this guide, we'll delve into the req.baseUrl property, a feature that helps you retrieve the base URL of the currently mounted router.

💡 Syntax

The syntax for accessing req.baseUrl is straightforward within a route handler:

syntax.js

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const baseUrl = req.baseUrl;

baseUrl: The variable containing the base URL of the currently mounted router.

❓ How req.baseUrl Works

The req.baseUrl property in Express.js allows you to retrieve the base URL of the router on which the middleware or route handler is executed. It is particularly useful in scenarios where routes are mounted on a specific path, providing insight into the portion of the URL that led to the execution of the middleware or route.

example.js

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// Assuming the router is mounted at '/api'
const express = require('express');
const router = express.Router();

router.get('/info', (req, res) => {
  const baseUrl = req.baseUrl;
  res.send(`Base URL: ${baseUrl}`);
});

// Mount the router at '/api'
app.use('/api', router);

In this example, accessing /api/info would result in the output Base URL: /api, demonstrating how req.baseUrl reflects the mounted path.

📚 Use Cases

Route Prefixing:

Use req.baseUrl to dynamically determine the route prefix, allowing for flexible route handling based on the mounting path.

route-prefixing.js

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// Mount routes with a prefix
const adminRouter = express.Router();
adminRouter.get('/dashboard', (req, res) => {
  const baseUrl = req.baseUrl;
  res.send(`Admin Dashboard accessed via: ${baseUrl}`);
});

// Mount the router at '/admin'
app.use('/admin', adminRouter);

Shared Middleware:

Leverage req.baseUrl within middleware functions to log information specific to the base URL under which the middleware is applied.

shared-middleware.js

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// Shared middleware for logging
const loggingMiddleware = (req, res, next) => {
    const baseUrl = req.baseUrl;
    console.log(`Request for ${baseUrl}`);
    next();
};
  
// Mount middleware for all routes under '/api'
app.use('/api', loggingMiddleware);

🏆 Best Practices

Context-Aware Routing:

Utilize req.baseUrl for context-aware routing, allowing your application to adapt its behavior based on the base URL.

context-aware-routing.js

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app.get('/products/:id', (req, res) => {
  const baseUrl = req.baseUrl;
  const productId = req.params.id;
  res.send(`Product ${productId} accessed via: ${baseUrl}`);
});

Understand Router Hierarchy:

When dealing with multiple routers, be aware of the hierarchy of mounted routers to interpret req.baseUrl accurately.

router-hierarchy.js

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const express = require('express');
const app = express();

const routerA = express.Router();
const routerB = express.Router();

routerA.get('/info', (req, res) => {
  const baseUrl = req.baseUrl;
  res.send(`Router A: ${baseUrl}`);
});

routerB.get('/info', (req, res) => {
  const baseUrl = req.baseUrl;
  res.send(`Router B: ${baseUrl}`);
});

app.use('/routeA', routerA);
app.use('/routeB', routerB);

In this example, accessing /routeA/info and /routeB/info would yield different req.baseUrl values.

🎉 Conclusion

The req.baseUrl property in Express.js provides valuable insights into the base URL of the currently mounted router, offering flexibility and context awareness in your route handling. By understanding and effectively using req.baseUrl, you can enhance the precision and adaptability of your Express.js applications.

Now equipped with knowledge about req.baseUrl, go ahead and optimize your route handling strategies in Express.js!