Invalid Parameter Error in NextJS

In previous lessons, we returned a 404 error when the route for a given URL was not found. However, in the case of a dynamic route, a situation may arise where the route exists, but the parameter value is incorrect.

Let's look at an example. Suppose we have a route like this: /user/:id.

Let's also assume we have a users object:

let users = {
	1: 'user1',
	2: 'user2',
	3: 'user3',
	4: 'user4',
	5: 'user5',
};

Suppose we want to display a user by their id:

export default function User({ params }) {
	return <p>
		{ users[params.id] }
	</p>;
}

Obviously, the id in the URL cannot be any value, but only one of the keys in our object. An attempt to access a non-existent address like /user/6 should result in an error being thrown. Let's fix our component code and display an error message:

export default function User({ params }) {
	if (users[params.id]) {
		return <p>
			{ users[params.id] }
		</p>;
	} else {
		return <p>
			user not found
		</p>;
	}
}

However, this is not enough. Because in this case, we are accessing a non-existent page, which means we should return an HTTP status of 404. This is done using a special function notFound, built into NextJS.

Let's import this function:

import { notFound } from 'next/navigation';

And now we will call it when the parameter value is incorrect:

export default function User({ params }) {
	if (users[params.id]) {
		return <p>
			{ users[params.id] }
		</p>;
	} else {
		return notFound();
	}
}

The full code of our component will look like this:

import { notFound } from 'next/navigation';

let users = {
	1: 'user1',
	2: 'user2',
	3: 'user3',
	4: 'user4',
	5: 'user5',
};

export default function User({ params }) {
	if (users[params.id]) {
		return <p>
			{ users[params.id] }
		</p>;
	} else {
		return notFound();
	}
}

Solve the described problem in your components.