Accessing Query String Parameters in Express.js

When working with Express.js, accessing data from the URL string can be critical to the functionality of an application. In this context, we discuss how to access the query string parameters in an Express route, with req.query being the correct method.

Understanding req.query

req.query is a property in Express.js request object which is filled with a parsed version of the query string. The query string refers to the part of the URL that comes after the ? symbol and is usually composed of key-value pairs.

When we need to read the value of a parameter from the URL or query string, req.query is used. For example, if we have a URL like http://www.mysite.com?name=John, req.query.name would be John.

You can access the whole query string object by just calling req.query. This returns an object with the keys and their corresponding values from the query string.

Let's see an example of how it works:

app.get('/users', function(req, res){
    console.log(req.query);
});

If we hit the endpoint /users?name=John, the console output would be { name: 'John' }.

Express.js' req.params vs req.query

It's important to understand the difference between req.query and req.params. They may sound similar, but work quite differently.

• req.query is used to access the query parameters. The values are sent in the URL after the ? symbol and are separated by &.
• req.params is used to access dynamic parts of the URL path. These are defined in the route, like /users/:userId.

They are both used to send data from the client to the server, but the differences become obvious when you begin building routes that need to handle dynamic data.

Conclusion

Hence, correct way to access query string parameters in an Express route is via req.query. Remember, looking for data in the right object is crucial for your Express.js application to work correctly. Understanding the difference between req.query and req.params will make your job easier when dealing with HTTP requests in Express.js.