Table of contents
In this article, we will explore how to work with query parameters and URL parameters in Express.js. Understanding how to handle these parameters is crucial for creating dynamic applications that respond to user input.
What Are Query Parameters?
Query parameters are a way to pass additional data to the server via the URL. They are appended to the URL after a question mark (?) and are separated by ampersands (&).
Example of Query Parameters
A typical URL with query parameters looks like this:
http://localhost:3000/search?query=express&type=framework
In this example, query and type are the query parameters.
Accessing Query Parameters in Express
To access query parameters in an Express route, you can use req.query.
Example:
import express, { Request, Response } from 'express';
const app = express();
const PORT = 3000;
app.get('/search', (req: Request, res: Response) => {
const { query, type } = req.query;
res.send(`Search query: ${query}, Type: ${type}`);
});
app.listen(PORT, () => {
console.log(`Server is running on http://localhost:${PORT}`);
});
If you navigate to http://localhost:3000/search?query=express&type=framework, the response will be:
Search query: express, Type: framework
What Are URL Parameters?
URL parameters, also known as route parameters, are defined in the route path. They are part of the URL and can be used to capture specific values.
Example of URL Parameters
A URL with URL parameters looks like this:
http://localhost:3000/users/123
Here, 123 is a URL parameter representing a user ID.
Accessing URL Parameters in Express
To access URL parameters, you can use req.params.
Example:
app.get('/users/:id', (req: Request, res: Response) => {
const userId = req.params.id;
res.send(`User ID: ${userId}`);
});
If you navigate to http://localhost:3000/users/123, the response will be:
User ID: 123
Combining Query and URL Parameters
You can combine both query and URL parameters in a single route to create more dynamic endpoints.
Example:
app.get('/users/:id/orders', (req: Request, res: Response) => {
const userId = req.params.id;
const status = req.query.status;
res.send(`User ID: ${userId}, Order Status: ${status}`);
});
If you navigate to http://localhost:3000/users/123/orders?status=pending, the response will be:
User ID: 123, Order Status: pending
Validation and Handling Missing Parameters
When working with parameters, it's essential to validate their presence and type. You can use middleware or inline validation for this purpose.
Example of Validation:
app.get('/users/:id', (req: Request, res: Response) => {
const userId = req.params.id;
if (!userId) {
return res.status(400).send('User ID is required');
}
// Further processing
res.send(`User ID: ${userId}`);
});