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Now that we've seen a couple of examples of raise, I want to walk through some kind of corner cases

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around them.

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So essentially I want to discuss why we care about these rates.

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Like what's so big a deal about a raise in typescript that we're making this into a separate topic?

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Well, here's why.

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When we work with the raise, typescript, we got a couple of different advantages and a couple of different

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downsides as well.

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So first off, TypeScript can help us when we make a type turei by helping us do type inference whenever

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we are pulling a value out of an array.

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Let's see a quick example of that.

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Zoback back over inside my code editor.

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I'm going to put a little comment down right here and I'll say help with inference.

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When extracting values, so in other words, if we look at our carmaker's array right here, we know

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that it is an array of strings, typescript knows that as well through type inference.

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So that means that if we ever pull an element out of this array, either by using, say, the pop method

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or by direct index access, typescript will know that we are going to be pulling out a string and help

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us with type inference with the new variable that we're assigning this this value to.

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So let's take a look at an example of that.

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Let's say that I'm making a new variable right here and I'm going to call it something like car.

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If I then take car makers and do an index access to it, I can now hover over car and you'll see that

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type inference has come into play in.

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TypeScript knows that this variable is going to be a string.

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It knows this because it knows that carmakers is an array of strings and we just pulled one value out

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of it.

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Likewise, this also works if we try a pop method, so let's say we've got my car, would you like car

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makers pop like so to remove the last element in the array, once again, TypeScript knows that carmakers

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has an array of strings.

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So when we call Pop, it's going to return an instance of a string so we can once again hover over my

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car and we see up.

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TypeScript has correctly inferred that my car is going to be a string.

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All right.

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That's one benefit of making use of a raise and typescript secondly, typescript can help us prevent

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or help prevent us from adding in incompatible values into an array if we have correctly type the array.

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So, for example, back over here once again, we can say prevent in compatable.

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Values.

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So once again, if we take our carmakers away right here, that only contains strings and we tried to

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add in some element that is not a string like let's say a number will very quickly see an error message.

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TypeScript is telling us here, hey, you're trying to put in a number to a collection that is only

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supposed to contain strings.

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So that's going to help us from putting in dissimilar elements into one single array.

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And once again, if we want to have multiple different types in an array, we definitely can do that,

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but we have to use some special syntax to do so.

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We'll take a look at an example of that in just a moment.

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All right, third, any time we declare an array, we get a lot of help with built-In functions like

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map for each reduce and so on, whenever we are iterating over a collection of elements.

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So, for example, if we look back over once again.

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We get help with map or for each and reduce, so, for example, if we do car makers map, we can add

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in a function rakia that will be called with every element in the array.

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So I'm going to receive each car as a string.

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And from this I'm going to return, say, a string as well.

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We'll just do a straight pass through here, so I'll take the car and return it immediately.

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So TypeScript is going to make sure that the value that we are putting into this function right here

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will be a string.

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And so because of that, because TypeScript knows that Corey is going to be a string, we get access

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to a lot of different autocomplete on the variable that comes in here.

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So, for example, if I put in a dot right after car, I can then see the autocomplete appear with all

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the different methods that belong to strings.

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So, for example, I can do a two upper.

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Case like so.

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So any time we start working with bat for each reduce or any similar, Helper's typescript is going

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to give us autocomplete on the variable being passed into this function right here, which is a nice

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little benefit.

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All right, now, the last item we're going to talk about right here is that we can, in fact, put

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different types of elements inside of an array.

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Let's take a quick pause, though, because there's a couple of different corner cases around this and

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some interesting syntax we need to understand at the same time.

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It's a quick pause and I'll see you in just a minute.