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If statements need Boolean values between those brackets

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and we also called those values just booleans

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and that's another value type besides strings

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and numbers and objects and arrays,

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Boolean values are a special value type

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that have exactly two possible values, true or false.

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So it's like yes or no, just to that,

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it's called true and false.

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And these two values are our Boolean values,

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we can work with in JavaScript.

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So whereas a number can be any number

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and a string can hold any texts.

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A Boolean value can only hold either true or false.

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And these are useful, these values,

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if we have a yes or no question.

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And when do we have such a question?

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Exactly. If we have an "if statement",

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because we want to execute some code,

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to code inside of these curly braces in this if statement,

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if a certain condition is met. So if this year says, yes,

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then we want to execute the code. If it says no,

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so falls in the Boolean world,

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then we don't want to execute this.

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Now we could directly add true here

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as a value and very important

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Here we don't have quotes because,

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we don't want a string like this instead,

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true and false are values,

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which are built in as keywords like this.

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And if I would set this to true then this would execute.

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If I now a save that code

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and I open my console here, we see how low.

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And on the other hand,

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if I set this to false and I saved this,

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then we don't see anything. Because then, that code in the,

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if statement does not execute,

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because that does not answer the question,

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wherever that code would be executed.

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So if that code would be executed with true instead,

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it answers it with false, which means no.

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So if false then do nothing.

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If true, then execute this code.

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This is how you can read this.

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Now boolean values are super important in programming

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because we need them for control structures like this,

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because we need them for "if statements".

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And as you will see in most programs that you write,

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you will have some parts of your code

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that are actually conditional,

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that need "if statements" so that you can control

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which code should run, and if it should run at all,

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but you will typically not.

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Hard-code true or false into your if statement as we are

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currently doing it, why not?

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Well, because then the entire if statement is redundant.

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This will always be true, and this will always be false.

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So that's not too useful.

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I only did that to introduce Boolean values

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In stat, you will typically derive Boolean values

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with help of so-called comparison operators

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and also sometimes with logical operators.

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And I will, of course explain both types of operators.

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Up to this point, we did learn about those moth operators

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and the concatenation operator does plus,

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which we can use on strings

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comparison and logical operators

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are additional sets of operators,

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which we can use in Java script.

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But the whereas mathematical operators yield us numbers

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and the concatenation operator returns a string comparison

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and logical operators will actually give us Boolean values.

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And let's start with comparison operators here.

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Here, we got these operators,

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which we can use to compare values with each other.

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The first set of operators here is the equality operator

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and there we have two kinds of equality operators

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with two and three equal signs.

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And I'll show you the difference in a second,

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but basically we use these operators

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if we want to compare two values for equality.

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So for example,

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if we would want to check whether two is equal to two

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or two as a string, as equal to two,

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and you see that would actually give us false

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if we use that triple equals on operator.

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But again, I will explain it in greater detail soon.

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And you'll see a couple of other

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examples down there as well.

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This equality operator can be used to compare

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numbers with numbers, strings with strings,

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numbers with strings and a couple of other values as well.

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It also has a couple of gotchas, but again,

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we will see that through out the course.

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And in general, the deeper you dive into JavaScript,

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the more you will learn about those gotchas,

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but it generally works quite straightforward.

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You can use it to compare values for equality.

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And of course the examples here,

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I have hard-coded values only in reality,

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you would typically compare values that are entered

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by a user in some input field,

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from what you've got the value or what you fetched

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from some website or anything like that.

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Because otherwise, of course, if you hard code the values,

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you already know the answer in advance as a developer.

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These are really just examples here.

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Now the next set of comparison operators are these

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greater than, lesser than,

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greater or equal and lesser or equal operators,

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which allow you to do these exact operations where you

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can check whether five is greater than three and so on.

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It is worth pointing out that you can also use these

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operators on strings. And they're A would for example,

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be smaller than B because it comes earlier in the alphabet.

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So that's all the worth mentioning here.

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Now, the last set of comparison operators,

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which you see here are negation operators

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or operators that yield the inverse of what you're checking.

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So you can check if something is not true.

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And you'll see a couple of examples here.

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Please note that in the first line,

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I'm also using brackets so that for smaller,

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four is evaluated first and that would

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normally yield false because four is not smaller than four,

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but with the negation operator,

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the exclamation mark here I then get the inverse of bet.

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And the inverse of false is true.

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And that's how we derive that value.

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And that's also sometimes exactly what you need.

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Now, Sometimes you don't just have one check that

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you want to perform, but multiple checks.

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And then it's the overall result of combining

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all those checks and they have for combining

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all those Boolean values, which result from these checks.

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And that's exactly where logical operators can help you

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Here, we got two kinds of logical operators.

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We got the and and or operator and with,

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and we get true if both compared values are true

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and here are some examples

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for how that would behave

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and with the, or operator we get true.

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If one of the two values is true.

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So here it's enough.

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If one of them is true and you'll see some examples here,

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basically the same examples as on the left, just with,

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or instead of, and, and that's of course,

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just an overview and a summary.

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We are now going to explore these operators and play around

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with them in code and then see how we can use them in

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conjunction with if statements

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to do more useful things there