How do you access query parameters in an Express JS route handler?

Express JS is a popular web framework for Node JS, simplifies the development of web applications. One common task is accessing query parameters from URLs within route handlers. In this article, we’ll explore the fundamentals of working with query parameters in Express JS and demonstrate how to access and utilize them in your route handlers.

Prerequisites

• Node.js
• Express JS server

Understanding Query Parameters:

Before diving into the implementation, let’s briefly understand what query parameters are. In the context of a URL, a query parameter is a key-value pair appended to the end of the URL after a question mark (?). These parameters are often used for filtering, searching, or providing additional data to server endpoints.

Example:

https://example.com/search?query=express&category=nodejs

Accessing Query Parameters in Express JS:

In Express JS, accessing query parameters is straightforward. The req object, which represents the request being made to the server, contains a property called query. This query object holds the parsed key-value pairs from the URL’s query string.

Let’s look at a simple Express JS route handler that extracts query parameters:

Javascript

const express = require('express');
const app = express();
const PORT = 3000;

app.get('/search', (req, res) => {
    // Accessing query parameters
    const queryTerm = req.query.query;
    const category = req.query.category;

    // Your logic here using query parameters
    // ...

    res.send(`Search Query: ${queryTerm}, Category: ${category}`);
});

app.listen(PORT, () => {
    console.log(`Server is running on port ${PORT}`);
});

In this example, the route handler for the /search endpoint extracts the query and category query parameters from the URL. You can then use these parameters as needed in your application logic.

Handling Missing Parameters:

It’s essential to handle cases where query parameters might be missing. In the example above, if a user accesses /search without providing the required parameters, queryTerm and category would be undefined. You should add validation and error handling based on your application’s requirements.

Conclusion:

Accessing query parameters in an Express JS route handler is a fundamental skill for building dynamic and data-driven web applications. By understanding how to use the req.query object, you can easily extract information from the URL and leverage it in your server-side logic. As you continue to explore Express JS, mastering query parameter handling will empower you to create more robust and interactive web applications.