All about NextJS routing

Intro

• It has a file-system based routing mechanism
• When a file is added to the pages folder in a project, it automatically becomes available as a route
• By mixing and matching file names with a nested folder structure, it is possible to pretty much define the most common routing patterns
• Routing variations are:
  • Route with pages
  • Nested routes
  • Dynamic routes
  • Catch-all routes
  • Navigate from the UI
  • Programmatically navigate between pages

Routing with pages

It has a file-system-based routing mechanism.

1. Scenario 01: index.js file within the pages folder will map to the root (https://localhost:3000) of your domain.
2. Scenario 02: Pages are associated with routes based on their names. In the pages folder, about.js maps to https://localhost:3000/about and profile.js maps to https://localhost:3000/profile in the address bar.

Nested routes

1. Scenario 01: pages->blog->index.js maps to https://localhost:3000/blog
2. Scenario 02: pages->blog->first.js maps to https://localhost:3000/blog/first
3. Scenario 03: pages->blog->second.js maps to https://localhost:3000/blog/second

Dynamic routes

• To implement dynamic routes, you need to name a component by wrapping it with square brackets like [componentName].js and componentName will correspond to the dynamic value in the url
• pages->product->[productId].js maps to https://localhost:3000/product/1, https://localhost:3000/product/2 or even https://localhost:3000/product/100. The number/string after the /product/ in the url will dynamically correspond and map to [productId].js component and the number/string after /product/ can be found inside [productId].js component using the useRouter hook like this -

 const router = useRouter();
    const productId = router.query.productId; 
    // productId is the dynamic component’s name

• But if a number/string after /product/ in the url is matched with the name of a component already existing inside the product page, that component with the matched name will get priority over [productId].js and be rendered rather than [productId].js being rendered.

Nested dynamic routes

• To implement nested dynamic routes like https://localhost:3000/product/7/review/2, you need a folder structure like pages/product/[productId]/review/[reviewId].js. Note that this time [productId] is a folder, not a .js file.
  • So, pages/product/[productId]/review/[reviewId].js maps to https://localhost:3000/product/7/review/2
• In this mechanism, to achieve the functionality of https://localhost:3000/product/1, (only dynamic, not nested dynamic) you need a folder structure like pages/product/[productId]/index.js. You will find productId in the url dynamically in the index.js file.
• Thus you can implement dynamic nested routes by having dynamic segments in the folder name as well as file name.
• Speaking of dynamic multiple path segments, Next JS does offer another feature to handle the same. To know more about the feature, read the next topic.

Catch all routes

• This feature applies to scenario where the url contains multiple route segments like https://localhost:3000/docs/feature1/concept1
• The folder structure for https://localhost:3000/docs/feature1/concept1 should be pages/docs/[...params].js and inside [...params].js you can use useRouter to get both feature/ and concept/ or even more to it like below -

    const router = useRouter();
    const { params = [] } = router.query; 
    // assigned an empty array because initially it is undefined 
    // and may give an error in production
    console.log(params); // [ "features1", "concept1" ]

• After getting your dynamic route segments, You can then conditionally render your components or JSX elements like this -

const Doc = () => {
    const router = useRouter();
    const { params = [] } = router.query; 
    // assigned an empty array because initially it is undefined 
    // and may give an error in production
    console.log(params); // [ "features1", "concept1" ]

    if (params.length === 2) {
        return (
            <h2>Viewing docs for feature {params[0]} and concept {params[1]}</h2>
        )} else if (params.length === 1) {
        return (
            <h2>Viewing docs for feature {params[0]}</h2>
        )}
    return (
        <div>Docs home page</div>
    )};

export default Doc;

• But the folder structure pages/docs/[...params].js will give a 404 while trying to access https://localhost:3000/docs. To have a quick fix, you can put another pair of square brackets around [params].js, so the new folder structure is pages/docs/[[...params]].js and https://localhost:3000/docs does not give a 404 and works as expected.

Link component navigation

You can navigate in the UI using Link component offered by Next.js like this -

<Link href="product/2" replace >
     <a>Go to Product 2</a>
</Link>

Navigating programmatically

You can navigate programmatically using useRouter. All other routing variations are valid in this mechanism.

const Home = () => {
    const router = useRouter();
    const handleOrder = () => {
        console.log('Placing the order...');
        router.push('/product');
    };
    return (
        <div>
            <button onClick={handleOrder}>Place order</button>
        </div>
    );
};

Custom 404 page

To provide your custom 404 page, create a 404.js file in the pages folder.

Conclusion

So, that is all about routing in NextJS. Hope you liked it. Thanks for reading.