A Deep Dive into React's Component
Jul 30, 2023In the world of web development, one of the most common tasks is routing, i.e., navigating users from one part of a web application to another. Modern JavaScript frameworks like React simplify this task by providing a built-in component, <Link>, that handles routing in a performant and seamless way. This article provides an in-depth explanation of the <Link> component, primarily in the context of Next.js, a popular React framework.
What is <Link>?
<Link> is a React component that builds on the native HTML <a> (anchor) element by offering additional functionalities such as prefetching and client-side routing. It's the primary component for navigating between routes in a Next.js application.
In a basic usage scenario, you can import the <Link> component from next/link and use it within your function component. Here's an example where a <Link> component is used to navigate to a "dashboard" page:
import Link from 'next/link'
export default function Page( ) {
return <Link href="/dashboard">Dashboard</Link>
}
Props Available in <Link>
There are several props that you can use with the <Link> component. Here's a quick rundown of the most important ones:
-
href: This is the path or URL to navigate to. It's the only required prop. This can be a string (e.g.,<Link href="/dashboard">Dashboard</Link>) or an object to include a query string (e.g.,<Link href={{ pathname: '/about', query: { name: 'test' } }}>About</Link>). -
replace: This boolean prop defaults tofalse. If set totrue,next/linkwill replace the current history state instead of adding a new URL to the browser’s history stack. -
prefetch: Another boolean prop, it defaults totrue. If enabled,next/linkwill prefetch the page denoted by thehrefprop in the background, thereby enhancing the performance of client-side navigations.
Note: It's also possible to use HTML anchor tag attributes like className or target="_blank" as props with <Link>. These will be passed to the underlying <a> element.
Linking to Dynamic Routes
For dynamic routes, the <Link> component allows using template literals to form the link's path. If you have a dynamic route like app/blog/[slug]/page.js, you can generate a list of links using a map function:
import Link from 'next/link'
function Page({ posts }) {
return (
<ul>
{posts.map((post) => (
<li key={post.id}>
<Link href={`/blog/${post.slug}`}>{post.title}</Link>
</li>
))}
</ul>
)
}
Middleware and <Link>
Middleware is often used for operations like authentication or rewriting the user to a different page. When using <Link>, especially for prefetching purposes, you need to tell Next.js both the URL to display and the URL to prefetch. This is important to avoid unnecessary fetches to middleware and to ensure the correct route is prefetched.
Consider an example where a /dashboard route has authenticated (i.e., logged in) and visitor views. In your Middleware, you might have a function that checks for an authToken cookie and rewrites the user to the correct dashboard page:
export function middleware(req) {
const nextUrl = req.nextUrl
if (nextUrl.pathname === '/dashboard') {
if (req.cookies.authToken) {
return NextResponse.rewrite(new URL('/auth/dashboard', req.url))
} else {
return NextResponse.rewrite(new URL('/public/dashboard', req.url))
}
}
}
In your <Link> component, you would use both as and href props to manage the URL to display and the URL to prefetch:
import Link from 'next/link'
import useIsAuthed from './hooks/useIsAuthed'
export default function Page( ) {
const isAuthed = useIsAuthed()
const path = isAuthed ? '/auth/dashboard' : '/dashboard'
return (
<Link as="/dashboard" href={path}>
Dashboard
</Link>
)
}
In conclusion, the <Link> component is a powerful tool that enhances the routing capabilities of a Next.js application. By understanding its usage and nuances, developers can create applications with optimal performance and seamless navigation.
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