- What is Express Middleware? 2:22
- Middleware Sequence and Routing 5:11
- Review: Middleware Sequence and Routing 5 questions
- The `next` function and a Closer Look at Middleware 4:45
- Handling Errors in an Express App 3:56
- Review: `next` and Handling Errors 5 questions
- Error Handling Middleware 5:20
- Handling 404 Errors 2:34
- Review: Error Handling and 404s 5 questions
Preview
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Handling 404 Errors
2:34Now that we have a custom error handler, let's add a middleware function to handle 404 errors, and send them to the error handler.
A 404 signals that the user
requested a route that doesn't exist.
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Remember, when an app gets a request,
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it will go from one app.use call
to the next looking for a match.
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If it gets to the end without finding
a route and there are no errors,
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Express' native handler will send a 404
back to the client with some plain text.
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If we catch the request before
it gets to the end of the line,
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we can send users a better page.
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Check out Treehouse's 404 page, or Lego's,
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or my personal favorite, GitHub.
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We can give our users
a less scary page too.
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Let's write some middleware to
handle 404 errors in our app.
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We want to access the request at the end
of our app and before the error handler.
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So let's call app.use here.
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We're going to use the error
handler we wrote in the last video
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to handle the actual error.
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This middleware will
just be responsible for
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creating the error object and
handing off to the error handler.
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I'll create a new error, Not found.
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Then I'll set the error status code,
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To 404,
Before parsing it to the next function.
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Now, any requests that makes it
this far will run this function and
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trigger the error handler.
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The error handler itself will send
the page out to the user in that event.
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Let's try it out.
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In the browser,
I'll request a route that doesn't exist.
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Voila, now when our users go astray,
they will get a friendlier notice.
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We've covered the basics of Express now,
well done.
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Let's cement your knowledge in
the remainder of this course by
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finishing our flash card application.
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Are you ready to apply your knowledge?
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See you there.
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