Let's take a look at the solution to these challenges that we had in the Firebase case. I'm going to show you some example solutions to the case challenges. The first one is Number 2 here, how would we restrict users to specific e-mail domains, users that want to register? So the action there is probably going to be in our register user, was it? Yes, I believe it is. So down here, we have register user and I added a domain check this way. So this is a variable, a true-false variable of the link that gets the result of this function check domain, which takes as its input the e-mail that our user supplied. So down here, this is a little bit overkilling, you absolutely didn't need to include this, but I had a separate function get domains, that's down here. It's a little even silly as it's written, but that returns a set of domains that are the okay domains. You also didn't need to support multiple domains here if you just did it against the one domain. That's also fine. This domain, the domain that our user submitted, I get by saying, take the e-mail and then dot replace it with this regular expression, which is going to extract the domain portion. This is a thing called a regular expression, but I've just got this from Googling JavaScript extract domain portion of e-mail or something along those lines. For as long as you're comfortable enough with it, that's fine. You don't even know what all this syntax here means. Then, I found this sample code in a similar way, but this basically says, If you find in the set of strings or items this item, then return true otherwise return false. So this is basically says, if you can find this item x in this set of items, then return true, otherwise return false. It's essentially what this statement is doing. So that's how we get our result back. If we go back up here, if not check domains, in other words, if this check fails, then we're going to show them a descriptive error, otherwise we're going to just proceed. So if we want to see that working, I'll try to e-mail or try to register at the cowana@darden.virginia. If I click Register, indeed I get this descriptive error. Okay. So again, that's one way to approach the solution and the user experience as described, but there are lots of other cool ways to do it. So if you didn't do it exactly this way, that's fine. As long as you think that your solution is workable and you've provided a good user experience, that is okay. So let's look at Number 3 here. Basically, we have this idea that texts are going to come in and just try to sign into this, like they're used to signing on to all the other systems but they can't, because it's a stand-alone system for now. So we want to return a more descriptive error when they log in. So the action there is probably going to be around our login user function. So what we would want to do is when they log in, we would just want to update that alert that had that just simple login text with something more descriptive like, I just paste it in the thing from the case here. We might want to keep this error message thing or we might not. So if I try this and I do this and I click log In, then here I get this now updated alert. Now, you might want to do something especially given the other item, you might have done something even cooler here like, for example, made this conditional and only show them this alert if they're coming from one of the valid domains back there, which actually is a interesting reason to have separated out the get domain function from the other function. But if you did it this way, that it's fine, it's a great start and that's fine. So just to clarify the ideas like maybe you would want to make this say, we're only returning this alert if they're coming from this one certain e-mail domain, what we think is the each valid each back in a hurry domain. But if there's some random from some who knows where, then just show them a general error like that password. All right. So those are some ideas. Again, these were just for practice. Like this thing, for example, if you actually wanted to do this, you would want to send the users a confirmation e-mail first to validate that they really have that e-mail domain in questions probably. Something you've gotten from various sites, and in fact, Google Firebase supports that out of the box, but I didn't want to make the solution overly intricate. So those are some ideas on how to approach these solutions in the case, you've got in here, and you looked at this code, then that is great. You probably have a much, I'm sure that you have a much, much better idea of how to build real applications of substance from HTML, CSS, and JavaScript.
