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So now did we know about typescript fundamentals and how it differs and all is related to JavaScript.

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Let's dig a bit deeper into the different core types typescript knows the number is the type we see

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here.

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And as I explained there is no difference between integers like the five here and floats or doubles

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as it would be called in other programming languages like the 2.8 here.

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Indeed in JavaScript and the same is true in typescript all numbers are floats by default.

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So for JavaScript and dev for all of our typescript there is no difference between 5 like this and 5

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like this it's the same number essentially.

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Now besides numbers we all to have other core types and that would be strings.

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So text and boolean is let's all to have a look at those we actually saw.

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All of those in action here in this if statement already which we learned is a bit redundant.

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Nonetheless this here would be a string although of course 5 with quotes would be a string because it's

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text and the result for example of this comparison here.

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That would be a boolean this operator the triple equals sign or the negated equality operator here that

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produces True or false.

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And of course we can ever produce it dynamically enough if check which we'll of do or we initialize

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a variable with a true or false value.

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So let's do both here.

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Here we could add a new constant print result and set this to true for example.

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And just to make it really clear this could be a variable as well it doesn't have to be constant can

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be a variable which you would create with let in JavaScript.

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But since I don't plan on changing it here I'll go with a constant and we could pass this as a third

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parameter here.

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Let's say we pass in print result which holds true here.

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Now we immediately get an error of course because our add function does not support a third argument.

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We see expect the two arguments but got three.

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So therefore we have to make sure we support a third argument.

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And there we could add a show resolve parameter you could name it print or assault here as well.

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I'm going with show result to a wide confusion regarding the naming but technically these two names

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would not clash.

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So here I'll name it shall result.

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And I want to make sure that this is of type boolean by setting this to boolean again by adding a colon

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after the parameter here and then by adding the name of the type.

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Now this function accepts does and now what we can do is we can add a if check here and check if show

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result.

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If this is true we can of current course compare it to true but as you know in JavaScript you can all

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just pass in the true or false C value here and JavaScript Bill evaluated and if this yields true somehow

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or a truth value in general then we'll make it entity of block.

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Otherwise we won't.

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And let's say we do make it in here and then I want to console log and 1 plus and 2 otherwise in the

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Ellis case if we don't make it in there then I want to return this.

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So now does is a function which sometimes returns a value and sometimes does not return a value but

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output it immediately.

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Now you could argue if you want to write such a function which is kind of unpredictable or which might

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behave unexpectedly if you are passing and true here.

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But here we're doing it.

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So this function only sometimes returns sometimes it also does not return but instead just locks something

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to the console.

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Now here we can't actually call at just like this and don't need to store it in result and don't need

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to console log result because with print result set to true at itself.

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So the function itself will print the result.

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Hence if you know saved it and we recompile our apt yes file here with the TSC command.

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Once this is done the page will reload and we still see our output here.

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But now it's coming from line 6.

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And if we have a look.

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Line 6 is indeed inside the function.

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So this is a boolean.

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Now let's say we want to customize the output and therefore we have a result phrase constant here where

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we say result is colon and then some whitespace and we pass that in as foo as well with result Frasier.

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Well then we could expect this as an argument here as well phrase which should be of type String.

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By adding a colon and then string is the name of the type.

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And now we could use that phrase to output it as part of our result output.

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If we're printing the result right into function so then here we could have phrased plus and 1 plus

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and 2 and if we do that and we recompile by repeating that command we'll see that this phrase is part

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of the result but we also now reintroduce the old back because I have a string which I combined with

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two numbers.

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Everything is converted to a string here and that's not what I want to a white does in this function.

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We could add a result variable here or a result constant and store our result here.

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This will now be treated in a mathematical way because only numbers are involved and then a heater.

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We could combine that with phrase or just return it.

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And now since this is never directly calculated to gather with a string this will always be a number.

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And yes then here does number of combined with a string will be converted to a string.

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But since the mathematical calculation finished before that will have the right result.

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So now if repeat dad at a recompile we get the right output.

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So now these are the core data types and action.

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Let's now make sure we fully understand how types are assigned and also why we don't explicitly assign

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types down there.