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Hello, friends, who won our last lesson, we talked about data types in typescript, so now I want

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to carry on with that concept in this particular lesson.

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So we talked about the enum keyword last.

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So we'll start with the void type in this lesson.

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As you already know, we use the void type in functions that do not return any value, so it simply

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define a function.

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And a console print, hello.

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And if you wish, you can return a different value.

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However, if we come in here and define the function as void, then returning will give us an error

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because we specify that we will not return any value by making the function void.

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So if we don't want to return any value and we want to do an operation there, we can use the void type

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to print something like here.

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All right, now let's get into, well, briefly, the undefined type, actually, what this data type

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means.

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So we've defined a number variable, but.

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If we've not assigned any value to this variable, this variable will be undefined.

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But if we come in here and assign a value here, then undefined will disappear.

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You know, the data types similar to undefined is the null type, and we usually encounter these and

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database errors.

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So I should say that we've defined a class, but.

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We haven't shown any references like this, and when we want to access this class, the result will,

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of course be no.

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Because we do not provide any reference.

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So that's that's that for data times, but before we finish the lesson here, I want to talk a little

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bit about data assertions.

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To evaluate the situation, I'll first create a variable and define a string expression.

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So look here, we can see that our variable now is a string.

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Now, if we write our variable and put a dot.

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We can see the string methods that we can use.

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Thus, we can do different operations on this variable, for example, when we well, we can capitalize

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all the letters here or.

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We can use the length of this string expression.

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And here I'm assigning the character length of the string expression to a different variable like this.

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So there's no problem with the transactions that we've done so far.

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So what will happen if I change the variable that I first define?

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Well, this variable is no longer a string.

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It's an any variable.

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When we put a dot here again and look at it.

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We can't use a previous method because those methods are valid for string variables, so in order to

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fix this, I write the type I want to convert between the lesson and read it in signs.

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And I put this expression in parenthesis.

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And as you can now see, when I put a dot, I can see the method.

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So in this way, we have converted a variable that is any to a string variable.

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So here, you definitely need to pay attention to the variable that we want to transform and the variable

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here must be the same.

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Oh, get an error if I come in here and right, no, right, because this is a stirring expression.

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So we can write this expression differently as follows.

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So define another variable and I'll write the name of the first variable.

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Then right as string inferences.

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And as you can see, we can now recognize that they are string method's.

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So we can make the type conversion into different forms of writing.

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And that said, I think we're done now, so in our next lesson, we're going to start functions.

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All right.

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See you then.