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Now we understand how if statements work

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and how we can use comparison operators

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to check different conditions.

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There is a little extension, some extra knowledge

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you should have about Boolean values

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and if statements though, which I want to dive in now.

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And for this, I switched back to including

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the conditional code JS file here in the index HTML file.

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And in this conditional code JS file,

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I now want to show you a different way of using

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Boolean values and of writing if statements,

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which is also very common in Javascript.

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Up to this point, we always derived Boolean values

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by writing comparison code like this.

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And that is super common.

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But sometimes you also have so-called flag variables,

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which have a true or false value stored inside of them.

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And an example could be that you're building a website

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where users can log in and hence in your Javascript code

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that adds a certain functionality to the page,

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you might be storing the current log in status of the user

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because your code execution depends on whether

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a user isLoggedIn or not.

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For that, you could have a constant here or a variable,

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doesn't matter, which you could name isLoggedIn,

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which is a kind of name we haven't used up to this point,

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but which is a naming convention you'll use very often

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when you store Boolean values,

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because you want to describe what's stored in a variable.

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And here I want to store true, let's say.

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So not the result of some comparison, not a number,

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not a string, but true as a value itself.

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And then isLoggedIn is a quite fitting name

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if this variable stores the answer to the question

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whether the current website visitor is logged in or not.

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So here I'm storing true. Could be false, doesn't matter.

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It's just an example in that variable named isLoggedIn.

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And now we might have some code that should only be executed

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if this is true.

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And here, of course, it's hard coded,

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but again, we could be fetching this from some other part

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of this website and hence this could be dynamic.

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Let's imagine it is.

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Now we can write a if statement and we can, of course,

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then for example, console log user is logged in.

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We could do that.

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Now in this condition, we now might want to check

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if isLoggedIn is true or false.

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And for that, we can of course compare isLoggedIn

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to true and say this code should execute if isLoggedIn,

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this variable, has stored true as a value.

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That would work and there's nothing wrong with it.

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But keep in mind this condition here, in a if statement

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or also in an elseif block, of course,

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wants a Boolean value in the end.

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And we use comparisons like this,

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or like this because those comparisons do yield

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Boolean values.

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Now isLoggedIn actually already has

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a Boolean value stored.

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So this is kind of a redundant comparison.

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We can also just write if isLoggedIn like this.

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And if that's true, which in this case is,

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this code will execute.

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If this would be false, then this code would not execute.

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So if I save that, I get user is logged in here.

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Now let's say we would want to have the opposite check.

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And we want to say user is not logged in here.

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Then we might want to check whether isLoggedIn is false.

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And again, we could therefore write this

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and that would be correct, but we can also shorten this

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and just write if not isLoggedIn

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with that negation operator,

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this exclamation mark.

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With that we're saying, if this is not true,

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then this code should execute.

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Here, of course, it is true.

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And therefore if I save that, we have no output from that

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if statement here because we don't make it

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into this if statement with this condition and this value.

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But knowing that you can store Booleans in variables

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as I'm doing it here, and how you should then name

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these variables, that you should name them

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as if they answer a question, and that this is also

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a common thing to do and how you can then

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use these Boolean values in if checks, that is important.

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Because again, that's also a certain way of working

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with Booleans and if statements,

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which you will see a lot in web development.