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In this video.

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Let's finish up with the error handling.

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So we are going to create a function whereby we are going to use it to throw an error and going to catch

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inside the global error handler here.

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So inside the utils, let's create one file and I'll call this one as app error dot JS.

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And for this we can use a class or a normal function.

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So let me stick to using normal function.

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So we're going to be as cost app error is equal to and for this error function here, we will pass in

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the message that we want to send to the global error handling and then the starters code.

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And for this, if we don't provide it, we have access to it inside our global error handler here as

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500.

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So the most important one here is the message.

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So we need to add the message to the error class in JavaScript.

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So you're going to make use of late and then the error is equal to new than the error class.

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And here it takes only one argument and that is a message.

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So here we can add additional properties like the stock trace.

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So here make use of error dot stock and is equal to the error dot stock.

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And the next one going to be the status code, going to be error, the status quo.

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I want to add this one also as status code.

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All right.

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So in case we have one, then you go ahead and use it.

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Otherwise, you're going to use 500, as we did inside the global zero hand line.

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The last step is that I need to return the error from here.

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As tax and less export module exports is equal to the app error.

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So before using it, let's look at how it's going to work.

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First of all, we have our global error handler here and next is that this handler is going to watch

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anywhere in our code where we are returning or catching any error is going to send back the response

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to the user.

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So this global error handler here is going to look up at the app error and before the global error handler

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will get what came back from the app error here, unless we pass what came back from this one to next

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and next, we'll pass that response to the global error handler.

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So back to the user controller and here we go.

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Let's require the app error.

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So let me try to reserve it so I can have the auto import.

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Wouldn't it be as app error?

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So here we go.

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So to be able to catch any error, we are going to pass next as a third argument to this.

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And inside.

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Let me explain it.

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And inside here, we are going to return from here and we are going to call next and are going to pass

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in the function call as an error.

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Then you pass in the message.

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So what we want to send is user already exists or pass in here as first element.

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And remember this one also take second argument that is status code.

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So here we can provide 404 or 403 but for the meantime I will leave the one and I need to remove this

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one from here.

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So now if I make the requests to register with the same email, let's see.

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And now we can see that we have a valid error catching handle and we have the starters and which is

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for this one as feel when I make use of something here.

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Save it and let's register.

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And you can see the starters is called something, meaning that you go back what came back from the

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global era?

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Angela Yang So let me say again and let's look at the actual error that we want.

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Well, we couldn't get the message.

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I think we did some typing mistake here.

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Let's look hard.

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It's supposed to be one as message as that.

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So now let's send the request.

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And here you can see that we have the message called user already exists.

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And this is where we throw the error, which is this, and we have the valid status code.

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So this is how we can handle any error.

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So anywhere in our code we can throw any error.