Route & Query parameters in Express.js

Back to Express.js
Arjit Sharma
01 Min

Express provides built-in support for extracting values from URLs using route and query parameters. These features allow you to build dynamic routes, filter data, and create flexible APIs.

Route Parameters

Route parameters are dynamic segments in a URL that capture values from the path. Example - csprimer.in/user/1, csprimer.in/user/2 can be captured by /user/:id

Route parameters are typically used to identify a specific resource (like a user ID or product ID)

// Single route parameter
app.get("/user/:id", (req, res) => {
    const userId = req.params.id;
    res.send(`User ID: ${userId}`);
});

// Multiple route parameters
app.get("/user/:id/post/:postId", (req, res) => {
    const { id, postId } = req.params;
    res.send(`User ID: ${id}, Post ID: ${postId}`);
});

Route parameters are always strings, so convert them if you need numbers:

const userId = Number(req.params.id);

Query Parameters

Key-value pairs in a URL’s query string, starting with ?. Example - csprimer.in?name=Arjit&age=22

Query parameters are commonly used for filtering, searching, sorting, and pagination.

app.get("/search", (req, res) => {
    const { name, age } = req.query;
    res.send(`Searching for: ${name}, Age: ${age || "Not specified"}`);
});

On visiting http://localhost:3000/search?name=Arjit&age=25 , req.query would capture name and age

Note - Query parameters are URL-encoded automatically by browsers.

Conclusion

Route parameters help you identify specific resources, while query parameters let you filter or customize results.

Next →