Pratique du Shadowing: Learn Next.js Parallel Routes In 16 Minutes - Apprendre l'anglais à l'oral avec la vidéo

The app router in Next.js made routing more simple in some regards, but also more complicated by some of the new features that it added.

And one of those new, more complicated features is parallel routing.

Now, this is an incredibly important feature for you to understand to really take your applications to the next level, because it allows you to add extra performance by doing parallel streaming.

It also allows you to really easily render things dynamically or conditionally, which is great for something like authentication.

So if you're unfamiliar with parallel routing, it's definitely something you're going to want to learn if you want to master Next.js.

Welcome back to Web Dev Simplified.

My name is Kyle, and my job is to simplify the web for you

so you can start building your dream project sooner.

And if you want to really take your Next.js skills to the next level, I highly recommend checking out my complete Next.js course.

It's going to be linked down below.

It's part of my React.js course.

So just check out the link down below it's going to be the premium package of my React.js course

that includes the entire Next.js course.

Now in this video, I'm going to be talking about parallel routing, and I first want to talk about how it actually solves particular problems.

For example, right now, let's say that I have this dashboard page, which has just a nav at the top inside of my layout.

I'm rendering out my child page, which just is a really simple H2 that says dashboard, and then I'm also rendering out a user section and an article section.

And each of these sections has their own delay.

As you can see, the users is a three second delay, articles is five seconds, and then my dashboard is two seconds.

So when I refresh my page, you see I get these three different loading states showing up.

The first loading state for my dashboard is my loading.tsx file, while for my users and my articles, it's using the suspense boundary to load my information.

And this works perfectly fine.

I'm able to load all these routes in parallel, which means after two seconds, this one loads, then three seconds, this one, and finally after five seconds, my articles loads.

Now for really simple pages, this is probably going to be fine, but as your pages get more complex and you want to parallel stream multiple different complex things to your page,

there's going to be a much better way to do that, and that's with parallel routing.

So instead of having these components directly inside my layout, I can actually extract them out into their own folders, and they can work just like a normal page where I have my own loading state,

my own page, my own error state, and so on.

So I get all the power of having this route as its own page while keeping it embedded into a different page.

To do that, all you need to do is inside of the folder that you're currently in, so in my case dashboard, create a brand new folder, and you start this folder with the at symbol.

This allows you to say that you want to have parallel routes you render.

So in my case, I'm going to have an at users route, and inside of here, I'm going to create a page.tsx.

And all this page.tsx is going to do is just take this users component and bring it directly into here, and we'll export that as our default function, just like that.

And I'll call this my users page.

There we go and I'll make sure I'll get that wait function imported as well.

Then what I want to do is I want to go into my layout

and do the exact same thing for my articles section.

So I'm just going to copy this down.

I'm going to call this at articles.

And inside articles, I'm just going to change my wait to five seconds.

And this will say articles, and this will be my articles page.

So now I've essentially created two different parallel groups that I've created.

I have my articles group and my users group, and then I have my normal page group as well.

So inside my layout, instead of importing these components like this, I can remove all of that, remove this, remove this weight entirely, and all this suspense related code.

And instead, what I can do is where I'm getting my children being passed in, every single at group that you have is also going to be passed in.

So I have an at articles, and I have an at users.

And you'll even see I get autocomplete from TypeScript

because Next.js is smart enough to look at these folders and know that they are actually there.

So then what I can do is I can add in my articles, I can type that as a React node, and my users, and I can type that as a React node as well.

Give that a quick save.

And all I need to do is just render out those sections.

So users, articles, just like that.

And now if I add in a loading state for these, I'll actually be able to get that loading.

And the great thing about this is I can just create a new file called loading.tsx, export a default function, we'll call this loading users.

And in here, I'll just return an h2 that says loading users.

And I'll do the exact same thing for my articles, I'll just copy this file over and just change users to articles.

There we go.

So now if I give all these pages a quick save, and I go to my layout, you can see that my layout is drastically cleaned up.

But when I refresh my page over here, you're noticing that I'm getting the exact same results that I had before.

But the really great thing about this compared to what I had before is everything is much more componentized

because now I have this articles folder where everything related to my articles takes place.

I can even add in here, for example, an error.tsx page, and I can add in my own error boundary.

So this must be a client component.

And I'll just export default function error articles.

There we go.

And in here for now, I'm just going to return an h2 that says error, just to make it as simple as humanly possible.

So now for some reason, this actually throws an error.

So let's just come in here, throw a new error on this page.

And I give this a quick save and a refresh.

After that five second delay, you're going to notice it's going to throw an error and it's actually going to show me the text error instead, which is super great.

So again, it's super compartmentalized.

I have everything related to articles inside of this one single folder, everything related to users in this one folder, and everything related to my main dashboard section inside of this main folder here.

So everything has its own place, which means that if your code is complicated, it's much easier to figure out what's going on in each section.

But this isn't like super groundbreaking

because technically I could have done all of this the other way with everything in my layout file and so on.

And it wouldn't have been terrible, especially with simple code like this.

What makes this really powerful, though, is how you can take this even another step further.

Let's say, for example, I only want to render the article section of my page some of the time.

What I can do is inside of my layout, let's say I have a variable inside here that just says const render articles.

Let's set that equal to false.

So I only want to render my article sometimes.

Well, I can just come in here.

If render articles is true, then I'll render out my articles.

Otherwise, I'm just going to render out nothing.

So we can just do this really, really simple like that.

So I'm going to render out my articles if this variable is true.

Otherwise, I won't.

So when I do a refresh, you notice my article section is not rendered at all.

While if this was true, and I do a refresh, you'll notice that my article section is being rendered.

So this is a great way to conditionally render things, which is really useful, for example, with logging in users.

Let's say, for example, that this dashboard is something that you must be logged in in order to access.

Well, what I can do is I can just have a variable is logged in, you would get this from your database or something like that.

And by default, let's set that to false.

So here we're going to render out everything just like we normally would, but I'm going to wrap things in an is logged in.

So if I am not logged in, so if I'm not logged in, instead of returning all of this information down here, let's say I'm going to bring in a login page instead.

So I'm going to return login page, or we'll just call it login.

And I'm actually going to create a new parallel route for that.

So at login, just like that, let's create a brand new page.tsx.

which export default function login page and this will just return an h2

that says login page just like that there we go

so now here I can actually get that login

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and I can make sure I type

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that as a react node there we go so now

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if I'm not logged in I'm showing my login page otherwise I'm showing this page down here

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and actually remove those brackets just like that So now here, give this a quick refresh.

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And you'll notice right now it's not showing anything.

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That's because sometimes when you're dealing with parallel routes, you do need to actually restart your server.

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So let me just give my server a quick restart, and then we'll refresh our page.

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And we should see we are being redirected to the login page whenever we're not logged in.

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But if my login is set to true, for example, I've logged in my user, you can now see it's rendering out all the normal content on the page.

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So this is, again, a really powerful use case for this particular parallel routing.

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Now, the next thing I want to talk about with parallel routing is actually really cool, but by far the most complicated part.

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And that's how you deal with routes inside of your parallel routing.

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Let's say, for example, I want to be able to go to slash dashboard slash settings.

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And I want to be able to configure settings for each of these different sections, my dashboard, my users, and my articles.

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Well, this is really easy to do.

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First of all, I'm gonna remove all this login related stuff just so we have a little bit less complexity.

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So all that login code has been completely removed.

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We're just back to what we normally had before.

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And again, I'm just going to restart my server just in case I have any problems going on inside of it.

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So we're just going to restart our server and give that a quick refresh.

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You can see everything is working just like it was before.

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Now, what I want to do is I want to add in that new settings route.

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So I'm going to create a folder, call it settings.

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And inside of here, I'm just going to create a page.tsx.

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And I'm going to just export a function from here.

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Let's just copy all of this code.

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I'm going to make this incredibly simple, no waiting or anything like that.

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This is just going to say dashboard settings.

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There we go.

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And this is the dashboard settings page.

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So now if I go to slash dashboard slash settings, immediately we're going to get a 404 error.

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And the reason for that is because what happens

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when you have parallel routes is it's not only going to try to render your normal route in that settings folder,

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but also is trying to render out my at users parallel route and my articles parallel route.

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So I would need to create a folder inside of both of these with a settings.

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So we can create a settings folder in both of these, and both of these will need their own page.

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So inside of here, I'll create a page.tsx, paste that down, clean this up a little bit.

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So we have my articles, settings.

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There we go.

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Articles, settings.

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And I'm just going to copy that.

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I'm going to paste that down for the users one as well, and just change this to say users.

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There we go.

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So now, if I give that a refresh, that should hopefully work.

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And again, we might need to restart our server just because of the complexity here.

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Sometimes it makes you do this.

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And let's just give that a quick refresh.

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And as you can see, it looks like that worked.

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So now we have our dashboard settings, we have our user settings, and we have our article settings.

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Now in my layout in this section for some links, I'm just going to actually add in some links.

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So we're going to have a link that goes to my slash dashboard, just like that to close that off.

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Dashboard.

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And then we're just going to copy that link down to go to this settings as well.

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There we go.

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So now we have two links.

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So we can go to our dashboard page, which is going to load our dashboard, and we have our dashboard settings page.

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If we can go over to our settings just like this.

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Now you may notice that everything is not rendering properly.

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One thing that we may need to do is actually make all of these different functions async.

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So let's just come over here.

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We're going to make all of these async functions to hopefully see

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if that actually fixes the problem that we're running into here.

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It might also just be a problem with Next.js not being super happy with all of this in development mode, but you can see we have our settings page and our dashboard page, and it's still not quite working as we expect.

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And I believe it's just a problem with Next.js in development mode.

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To test this, we can npm run build to build out our project, and then we can just start this.

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So after this, we can say npm start, and that's going to start up essentially the production version of our application to see

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if these problems only exist inside of development.

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Again, some of these more niche features in Next.js are a little bit buggy in development.

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So here we're on the actual production version.

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When I click settings, you can see that works and when I go over to my dashboard here it works.

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So everything looks like it is working in the production version, which is great.

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So let's just go back to development so we can actually look at this as we're working on it.

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So we'll run the development version.

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I'll just give this a quick refresh.

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This is loading up the development version of the page.

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You can see we get all of our different loading text running.

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We'll wait for all

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that to finish just to make sure all of this is working as expected

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and then we'll jump over to the settings and I'll just do a refresh here to get that to actually show up.

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Now let's say for example that we didn't have a settings page for every single section

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because when we have a settings page for every section it obviously works fine

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But let's say our articles don't have a settings page.

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So inside of here, we're just going to delete this settings page entirely.

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Now, immediately when we do that and we refresh, we're going to get a 404 error because this page essentially does not exist.

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It also looks like I need to restart my server, so I'm just going to restart that development server.

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And then we'll do that again.

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We'll just refresh this section over here.

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And you can see that we're getting a 404 page immediately, and that's because there is no settings section for this article.

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What you can do instead is you can create a default.tsx file.

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This is going to run essentially any time that it cannot find a file for that route.

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So in our case, there is no page for our settings route.

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So it's going to render whatever is in here.

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So we're going to say export default function.

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And this is going to be called articles default page.

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And this is just going to return in H2 that says articles default.

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There we go.

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And we'll make that async just in case that helps with the actual development server.

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So if we just give this a quick refresh here, you can now see down here it says articles default because it's rendering whatever that default page is.

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So essentially, if I go to that settings page, do a hard refresh.

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So I'm coming to the settings page fresh, nowhere else, just directly to this link.

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You can see it renders that default version.

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This does work slightly differently, though, when you actually come to this page from another page.

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So for example, if I came from my dashboard page to my settings page, it would work differently.

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So let's bump ourselves into production to test that.

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So we'll say npm run build, and then we'll actually start up the production version because that allows this to work.

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We'll go over to the dashboard section.

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So we'll come over here to our dashboard, just like that.

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And once our page actually starts up in just a second, you can see we can refresh this and you can see it says dashboard users articles.

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And now when we moved the settings page, you can see we get the dashboard settings and the user settings, but our article stays exactly the same.

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So if you're moving from one parallel routing route to another parallel routing route, and the new route you're going to doesn't have a page for a specific section,

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such as our articles, what it'll do is it'll render out the old page that was already there.

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So it's just rendering this normal page right here until we go to a route that it has a page for.

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The only time that the default is shown is if you go to this page directly and not navigating through Next.

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So for example, I just refresh my page.

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You can now see it's rendering out that default version instead.

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and that's because I'm navigating directly to this page instead of using the linking inside of next.

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Now, if you don't like this behavior where it's actually showing you not the default version, so like when I go from dashboard to settings, you can see it doesn't show me that default version.

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If you don't like that behavior

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and you always want it to show a specific file when you don't have a route defined, what you could do is inside of our articles here, we could create a catch-all route.

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So essentially just putting the two dots before our name of our page, this is just going to be our catch-all.

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We can call it whatever we want.

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It really doesn't matter.

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and then inside of here we can essentially create a page that is going to look just like this default.

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So I'm going to paste this default in here.

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This is going to be our catch all page

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and this will say catch all just like that and we're just going to call this page.tsx.

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So now what's going to happen is essentially any time we go to a URL

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that is dashboards slash anything and it doesn't care how many levels nested that is, it's going to go into this catch all.

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So let's just close out of this real quick.

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We'll restart ourselves in development so we can actually see these new changes that we've just made

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and I'm going to go to my dashboard page and we're actually getting an error.

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That's just because I forgot to add in a period here.

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There needs to be three periods for the catch-all routes.

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Now let's actually run that in development.

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That was just my bad.

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Give that a quick refresh and you'll see it'll load our dashboard page just fine.

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Everything is loading perfectly fine.

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Now, if I go over to this settings page, you can see that I have both this default and this catch-all in place.

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So you can see when I click on settings and refresh it, you'll see it's actually loading the catch-all version instead.

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And that's because by default inside of Next.js, the catch-all route is always going to take precedence over this default page.

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So essentially, the reason you would want to use this catch-all is if you want to render the default every single time, no matter what, even when you're navigating around.

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So we can essentially just remove this default, we don't need it, and if we just run this as a production, so we can build our site, and then npm run start,

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we can see exactly how this works for navigating between different pages as well, because unlike in the default version, where it renders the old version when you navigate to a page that it doesn't exist for,

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this one is going to render the same page no matter what.

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So here you can see we have dashboard.

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It says dashboard uses articles.

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When I click on settings, you can see immediately we get that catch all route.

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And if we hard navigate to this page, we also get the catch all route.

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So that's kind of the difference between default versus a catch all route.

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They both serve very similar purposes, but they work a little bit different in practice.

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Now, if you enjoyed this video, you're definitely going to love my complete Next.js course.

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I'm gonna have it linked down in the description below.

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Like I said, it's part of my React.js course.

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So it's not only gonna help you master React everything that you need to know, testing and so on, but it's also going to make sure you master Next.js,

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both the app router and the pages router because they are both covered in the course.

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So if you want to take your Next.js skills to the next level, I highly recommend checking out that course.

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It'll be linked down in the description below and it is the React Simplified Premium Package.

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With that said, thank you very much for watching and have a good day.

✨ Vidéo recommandée

336 phrases

Vocabulaire et conseils d’expression pour cette leçon

Cette vidéo contient 257 phrases et 3922 mots à répéter en shadowing. La partie parlée dure 16:17. Le locuteur parle vite, environ 241 mots par minute : attendez-vous à des liaisons et à des sons réduits. 84 % des mots font partie des 3 000 mots les plus courants en anglais ; le reste mérite d’être vu avant de commencer.

Vocabulaire clé de cette vidéo

15 mots moins courants de la vidéo, avec leur prononciation et leur sens :

render /ˈɹɛn.dɚ/ (verbe) — rendre. To cause to become.
default /dɪˈfɔlt/ (nom) — défaut, non-respect. The condition of failing to meet an obligation.
refresh /ɹɪˈfɹɛʃ/ (verbe) — revigorer, rafraîchir. To renew or revitalize.
parallel /ˈpæ.ɹəˌlɛl/ (adjectif) — parallèle. Equally distant from one another at all points.
folder /ˈfoʊldɚ/ (nom) — dossier, chemise. An organizer that papers are kept in, usually with an index tab, to be stored as a single unit in a filing cabinet.
essentially /ɪˈsɛnʃəli/ (adverbe) — essentiellement, en essence. In essence: by nature.
log /lɔɡ/ (nom) — grume, tronc. The trunk of a dead tree, cleared of branches.
layout /ˈleɪ.aʊt/ (nom) — disposition, schéma. A structured arrangement of items within certain limits.
server /ˈsɝvɚ/ (nom) — serveur. A program that provides services to other programs or devices, either in the same computer or over a computer network.
react /ɹiːˈækt/ (verbe) — réagir. To act in response.
restart /ˈɹiːˌstɑɹt/ (verbe) — recommencer. To start again.
export /ˈɛks.pɔɹt/ (nom) — exportation. Something that is exported.
navigate /ˈnæv.ɪ.ɡeɪt/ (verbe) — naviguer. To plan, control and record the position and course of a vehicle, ship, aircraft, etc., on a journey; to follow a planned course.
complicated /ˈkɑm.plɪˌkeɪ.tɪd/ (adjectif) — compliqué, alambiqué. Difficult or convoluted.
component /kəmˈpoʊ.nənt/ (nom) — composant. A smaller, self-contained part of a larger entity. Often refers to a manufactured object that is part of a larger device.

Les verbes à particule que vous entendrez

log in (verbe) — s'identifier, se connecter. To gain access to a computer system, usually by providing a previously registered username and password.
check out (verbe) — mater, regarder. To record the departure or withdrawal of someone or something (such as guests, employees, books, etc.).
come over (verbe) — venir. To affect in a sudden, unprecedented or surprising manner; to overwhelm a person's ordinarily contrary impulse.
deal with (verbe) — traiter. To handle verbally or in some form of artistic expression; to address or discuss as a subject.
look at (verbe) — regarder. To observe or watch.
show up (verbe) — apparaître, se montrer se pointer. To appear, arrive, or attend, especially suddenly or erratically.
clean up (verbe) — nettoyer. To make an area or a thing clean; to pick up a mess; to tidy.
figure out (verbe) — cerner. To come to understand; to discover or find a solution; to deduce.

Prononciation à surveiller

Le locuteur utilise 121 contractions et formes réduites, comme I'm, we're, we'll. Prononcez-les sous leur forme courte, telles que vous les entendez.

Les sons « sh » et « zh »: refresh /ɹɪˈfɹɛʃ/, essentially /ɪˈsɛnʃəli/, dashboard /ˈdæʃˌboɹd/, conditionally /kənˈdɪʃənəli/, authentication /ɔːˌθɛntɪˈkeɪʃn̩/
Mots longs — placez bien l’accent: essentially /ɪˈsɛnʃəli/, complicated /ˈkɑm.plɪˌkeɪ.tɪd/, incredibly /ɪŋˈkɹɛdɪbli/, differently /ˈdɪf.ə.ɹənt.li/, complexity /kəmˈplɛk.sɪ.ti/

Comment s’entraîner avec cette vidéo

Écoutez la vidéo en entier une fois sans parler et notez les mots que vous ne connaissez pas.
Commencez à la vitesse 0,75×, répétez phrase par phrase, puis revenez à la vitesse normale quand cela devient facile.
Enregistrez-vous et comparez avec l’original, en faisant attention à des mots comme render, default, refresh.

La grammaire de cette vidéo

Les structures que le locuteur utilise le plus, avec les mots exacts de la vidéo :

Structure	Dans la vidéo
Phrases conditionnelles if + proposition, will/would + verbe — une condition et son résultat	If render articles is true, then I'll render
Voix passive be + participe passé — l’accent est mis sur ce qui arrive, pas sur qui le fait	be linked · being passed · is complicated
Propositions relatives who / which + proposition — une précision sur une personne ou une chose	conditionally, which is · page, which has · parallel, which means
Present perfect have/has + participe passé — une action passée qui compte encore maintenant	I've created · I've logged · has been

Qu'est-ce que la technique du Shadowing ?

Le Shadowing est une technique d'apprentissage des langues fondée sur la science, développée à l'origine pour la formation des interprètes professionnels. Le principe est simple mais puissant : vous écoutez de l'anglais natif et le répétez immédiatement à voix haute — comme une ombre suivant le locuteur avec un décalage de 1 à 2 secondes. Les recherches montrent une amélioration significative de la précision de la prononciation, de l'intonation, du rythme, des liaisons, de la compréhension orale et de la fluidité.

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Vocabulaire et conseils d’expression pour cette leçon

Vocabulaire clé de cette vidéo

Les verbes à particule que vous entendrez

Prononciation à surveiller

Comment s’entraîner avec cette vidéo

La grammaire de cette vidéo

Qu'est-ce que la technique du Shadowing ?