Route Parameters in Express

Route Parameters in Express

Route Parameters in Express

In this post, we will give you information about Route Parameters in Express. Here we will give you detail about Route Parameters in Express And how to use it also give you a demo for it if it is necessary.

In Express, route parameters are essentially variables derived from named sections of the URL. Express captures the value in the named section and stores it in the req.params property.

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

// ':userId' is a route parameter. Express will capture whatever
// string comes after '/user/' in the URL and store it in
// 'req.params.userId'
app.get('/user/:userId', (req, res) => {
  req.params; // { userId: '42' }

const server = await app.listen(3000);
// Demo of making a request to the server
const axios = require('axios');
const res = await axios.get('http://localhost:3000/user/42');; // { userId: '42' }

You can define multiple route parameters in a URL. In the below example, the Express route is /users/:userId/books/:bookId, so req.params.userId will contain the substring after /users/ and before /books/, and req.params.bookId will contain everything after /books/.

const app = require('express')();
// Route Parameters in Express
app.get('/user/:userId/books/:bookId', (req, res) => {
  req.params; // { userId: '42', bookId: '101' }
// Route Parameters in Express
const server = await app.listen(3000);
// Demo of making a request to the server
const axios = require('axios');
const res = await axios.get('http://localhost:3000/user/42/books/101'); // { userId: '42', bookId: '101' }

Why Route Parameters?

Route parameters have some convenient properties that reduce the amount of the validation you need to do versus using query parameters or request bodies:

  • A route parameter is never null or undefined. For example, a request to GET /users above will cause an HTTP 404, and not call the route handler for /users/:userId/books/:bookId.
  • A route parameter is always a string with positive length. For example, GET /user/42/books/ also causes an HTTP 404.

If you’re defining an HTTP API in Express, it is usually better to make a parameter a route parameter rather than a query parameter or a body parameter if possible. If your parameter is mandatory and doesn’t need to be an object, route parameters are generally the way to go.
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Espresso supports:

  • Route handlers, like ‘app.get()’ and ‘’
  • Express-compatible middleware, like ‘app.use(require(‘cors’)())’
  • Express 4.0 style subrouters

As a bonus, Espresso also supports async functions, unlike Express.

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I need more information on what you are looking for. Here are a few options for what you might mean by ‘express’:

  • Express train: A train that makes fewer stops than a regular train, and therefore travels faster.
  • Express delivery: A service that delivers packages quickly, usually within 24 hours.
  • Express yourself: To communicate your thoughts and feelings in a clear and direct way.
  • Express lane: A lane on a highway that is reserved for cars that are traveling faster than the other lanes.
  • Expresso: A strong, concentrated coffee.

Please let me know if any of these are what you were looking for. If not, please provide more information so I can better assist you.

Here are some examples of how to use the word ‘express’ in a sentence:

  • I took the express train to work today.
  • I ordered the package to be delivered express.
  • She expressed her anger by slamming the door.
  • The express lane was moving much faster than the other lanes.
  • I love the strong taste of espresso.

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