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And as far as the validation layer, we're going to use package by the name of Express Validator.

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Just keep in mind, yes, there are other packages as well.

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For example, you can use Joy, but in my opinion, Express Validator is super, super straightforward

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and therefore we're going to stick with this one and we'll start with another test route.

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So essentially, I just want you to understand the main concepts in isolation.

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And once that's the case, then of course we'll apply it to rest of the requests.

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So first of all, let's navigate to server and let's scroll up.

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So at the moment I have this post route to the home page where essentially we're just logging req.body.

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I believe we use this one to test out the express Json.

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Let's refactor it a little bit.

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I'm going to change the URL.

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I'm going to go with API version one because we already have the URL variable in the Thunder client.

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Correct.

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And I'm just going to go with the test.

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That's going to be my complete URL.

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For now, let's just grab the name since I know that I'm going to send that.

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So I'm going to go with name and I want to destructure it from req dot body.

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Then as far as the response, simply let's send back Res.json and instead of all this, we're just going

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to go with template string and we're going to go with Hello.

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And let's access the name.

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We're going to navigate to Thunder Client.

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And let's set up a new one again.

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This is just going to be a test one.

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So we can access the URL?

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Of course.

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Let's close the curlies.

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Then we're going to go with Test Body.

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Then let's provide name.

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And I'm going to go with Peter because why not?

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Let's send it.

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And it complains that we cannot find the root.

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And this is a good use case.

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So we go here with get an API version one.

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So why we have the error?

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Well, because this is a post road.

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And again, this is a good demonstration for the Morgan.

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You're right away.

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See that?

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Hey, listen, you're using the wrong method.

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So let's go here with post.

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Let's send it.

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And now, of course I have.

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Hello, Peter.

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Now, it's not going to be surprised if I go with Empty.

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String.

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Then of course, in my response I'll have this same result and this is what we want to fix with Express

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Validator.

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I want to set up a validation.

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If the name is not present, I actually want to send back 404.

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I don't want to send back 200.

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And again, just bear with me.

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We'll set up everything in a server and then once we have everything.

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In place, then we'll move it to a separate middleware and again apply to rest of the routes.

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First of all, let's import.

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We're looking for two things.

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We want to grab the body and the validation.

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Result.

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And both of these things are coming from.

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The Express validator package.

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Now, as far as the body, remember, so there are multiple places where we can check for values.

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For example, params.

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And therefore, since I know that I'm going to be checking for values in a body, I want to get the.

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Body export from express validator.

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And as far as the validation result, you'll see it in action in second.

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So let's scroll down.

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I think I can close the console for now.

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And here in between the controller and the URL, we want to set up express Validator as our middleware.

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So Express Validator is going to be sitting on top of our controller and if.

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The value is not present or it doesn't match our condition.

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Then we'll right away spit back the 400 error.

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And in order to set it up, we want to go here with the brackets.

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Then we need to invoke body.

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So essentially this is where we're looking for the value and the way it works.

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We just pass here the string.

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Now, of course, this string matches whatever we're expecting in the req.body.

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So since I'm expecting that there's going to be a name, that's why I type here, string of name.

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Later, when we check for lastname, when we check for job status and all that, of course we'll use

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the same string value and then we can nicely chain the methods that are provided and one of them is

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not empty.

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So essentially I'm saying, hey, listen.

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There has to be some kind of value in here.

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And what's also really cool, we can chain for specific errors, specific messages.

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So what am I talking about?

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Well, we can set up one main one, but also, for example, for not empty, I can say, hey, listen,

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name is required, but then when we'll add one to check the length, I can say, you know what the length

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should be between, let's say three and 50 and you'll see it in action in a second.

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So first, like I said, we can just keep chaining these methods.

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And the one we want to use is with message.

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So essentially this is going to be the error message we send back.

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So here we're going to go with name is required.

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And once we have this code in place, we actually want to add a function which will check for those

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errors.

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So essentially, yes, we'll have to middleware functions.

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So one is going to be where we'll set up our roles.

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And the second one is where we'll check for errors.

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If they exist.

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And if that's the case, then of course we'll send back the 404 or whatever error we want to send back.

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So in this middleware function, we want to access three things req res and the next.

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So when it comes to next, if everything is successful, we want to pass it to the next middleware.

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Otherwise, the request is going to stop over here in this middleware function.

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So next is a special one.

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And yes, of course, in this case, the next middleware technically is our controller, so that's the

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end of the chain.

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But normally if you set up next, that just passes on to the next middleware and that's something always

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you want to add because otherwise, again, this request is just going to stop over here in this function.

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Now, of course, we will invoke next based on the condition whether we have errors.

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But in general, try not to forget about the next and essentially.

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We want to set up a variable.

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I'm going to go over here errors.

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And this is where we want to invoke validation result and we're looking for the request.

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So essentially we pass in the incoming request.

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And since we already have this logic in place, it checks for that name in the body.

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Hopefully that is clear.

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And now, of course, I just want to log it just so we can see what's happening.

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And then we're going to discuss what methods we can use.

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So first, let's navigate to the new request.

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Let's send it one more time.

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So at the moment, yeah, the response is still the same.

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What I'm interested is the console.

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So notice over here I have this errors property and in here each error is represented with this object.

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Now what we're looking for is the message.

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So that's the one that we're going to send back.

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And what's really awesome, this instance has a few methods that we can right away use.

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For example, one of them is is an empty.

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So invoke it over here.

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We send it one more time and check it out.

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Basically, this is false.

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Now, what does that mean?

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Well, it means that we have the errors.

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So if is empty is true, then we're good to go.

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Then we can pass it on to the next middleware in our case controller.

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But if it's false, if it's not empty, that means we have errors.

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And of course, in that case we want to send back the error response.

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So let's set up the condition.

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I'll say if is empty is false, basically if we have the errors.

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Let's send back some kind of error response.

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Now, in my case, I'm going to hardcode the 400, but in the upcoming videos, when we set up the proper

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middleware, we'll actually invoke one of the classes we set up previously.

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Then we can also.

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Set up messages.

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So let me go here with some kind of variable error messages.

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And let me just make sure that the spelling is correct and that one is equal to errors.

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Again, this instance has this array method, which essentially turns it into an array and we can map

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over it.

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And what I want is, again, just to return that message property.

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Now, if you want to have different setup, of course you can change it around.

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But in my case, I'm just looking for that message property.

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So this one over here and again, this is built in this right away just turns it into an array and then

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we can iterate over and then when it comes to the response.

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Let's go here with return res dot.

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Again, we're hardcoding for now.

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We'll fix that in the middleware.

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Then let's go json.

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And since potentially I can have multiple error messages, I'm going to go with errors property and

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I'll set it equal to my error messages.

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So now if we go over here and if I send this one notice, I'll get back the errors and it's going to

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say name is required.

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And keep in mind, of course we can add more conditions.

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So let's say I add here, Peter, but I can go back over here where I have the angle brackets and I

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can just keep chaining my conditions.

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So for example, I can go with, you know, what is length should be, I don't know, let me go with

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something ridiculous and I'm going to go with 50.

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So we'll pass here the object and we'll say min is equal to 50.

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Again, something will change in a second.

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But just for testing purposes.

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And then remember, we can still change the message.

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So I'm going to copy and paste.

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Now we have with message and in here we'll just write something else.

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So I'll say name must be at least.

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And 50.

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And I'm not going to type characters because we'll set it up later and let's navigate back to the request.

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So technically we have the beta, but now we have a different error.

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And with this in place we have successfully added the express validator middleware to our test request.