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This lesson is all about comparison operators.

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We're going to look at Bulleen values, Truthy values, family values and a whole bunch of really neat

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things.

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So we did see earlier that we did use a comparison operator where we looked at the evaluation of content

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and seeing whether it's true or false when we are looking at booleans.

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So this is what a comparison operator does, is it allows us to ask a question and apply some logic

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so we can even do things like equal to which we've seen we can see greater than less than and these

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all return boolean values.

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So we're asking ourselves the question, is this comparable to that?

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And if it is, then we get a true value, and if not, then we get false.

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So they can only be one or the other.

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And those are where the booleans really shine.

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And also notice that when we do equal to that, we have two equal signs, sometimes three equal signs.

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If we're also including the data type.

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And this is important to note as when we're doing one equal sign, that's an assignment value.

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So that's an assignment operator and that's assigning a value.

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So to is to do the comparison so you can also use and combine and compare the two.

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So opening that up in the Mozilla developer network.

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So we've got all the different operators there and the assignment operators, their compound assignment

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operators that we've already seen.

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And then this is where we're looking at the comparison operators.

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So they're we've got the equal sign returns, too, if both are equal and they've got some examples

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here.

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So if three is equal to var one and if our one is actually three as well, that's good.

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Come back.

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True, otherwise it's false.

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We also have a not equal two, which is interesting because all you do is place the explanation mark

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plus the equals sign.

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So that also is looking for a true value.

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And if it's true, then it's going to run the first block a code within the condition.

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So that is something that if we've got three, not equal to four.

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And what's the answer to that?

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That's true.

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There's the strict equal.

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So this is also considering the data type.

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So meaning that if VAR is equal to the text, the string three and we've got a number three, then on

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those two equal sides, they are going to be equal.

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It's going to come back.

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True.

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But on the three equal signs, it's not going to come back.

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True.

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It's going to be false.

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And you can try all of this stuff out in the console so we could look at things like three equals three.

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And of course, that comes back.

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True.

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And if we do three equals and this is a string value that also comes back.

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True.

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And now if we try it with the third equal sine we see it comes back false.

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Three is not equal to and we do four.

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So that comes back true.

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And you could have some fun with this, play around with it, try out all the different values.

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So we see that that also returns back.

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True.

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And then within the statement then if we do return back true.

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Then that's when we run the function.

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You can also try different values.

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So you can say three is greater than six, which is false.

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We know that six is greater than three and that comes back true.

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70 is greater than or equal to 70 and that comes back true.

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So we know that 70 is not greater than true.

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So it comes back false.

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So there's a number of different combinations you can do and it really does take a little bit of time

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to get more familiar with these.

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This is where we've got the less than or equal to greater than or equal to.

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And they've got examples of how they work.

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If we're just doing the less than or greater than that, we only have the one simple there.

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We can also include the not so not within strict as well as not with an equal.

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So there's quite a few options and we can do a whole bunch of different types of comparisons.

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So what's being returned back is either a truthy or falsey.

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And we also saw this earlier when we were doing comparison between what boolean values, when we were

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adding them together.

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So we saw that booleans are either true or false and they could also be seen as a one or a zero and

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also values that are undefined.

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So if we have an undefined or a null or a zero or any NP being returned back for the variable, then

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that's going to come back as false.

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And otherwise, if we do have them and they are equal values, then they are true.

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So if it has a value, it's true.

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If it's set to true, it's true.

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And if it's got a value of one, then that's true.

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So those are the true things and the other ones were the falsies.

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So what we need to do in this challenge is check to see if a number exists and also check if it is greater

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than 50.

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So a message in the console.

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So first we're going to check to see if it exists for a variable.

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So get a variable, assign a value to it and do a condition checking to see if it's there and if it

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is output a message.

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And if there's no value, then we can do no doesn't exist.

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So use some of the.

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Falsies in order to indicate that it's not there, so null, zero false, et cetera, and then also

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check to see if the value is greater than 50.

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And if it is, then I'll put a message into the console so you can pause the video.

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And this is the solution to the challenge.

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So go ahead and pause the video and write up the solution within your editor.

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And I walk you through it coming up.

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Let's begin.

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So first of all, we need to have a number that we're going to be using so we can use five as our number

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that we're checking and we're going to check to see if none exists.

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And if it does, then we're going to run this blockquote and this is where we've got our console message.

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So if Chuck NUM exists, we can write check.

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None is true.

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So whatever it's returning back as true, then we get this message and next we want to also check to

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see if Chuck Numb is greater than 50.

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And I would put a message if it is greater than 50 and then we'll update the value of check number.

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And remember, it's even if it's 50, we're checking to see.

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So 50 is not greater than 50.

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So that's still going to be false.

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So keep that in mind as well.

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And then just to clarify what number we are working with will output in the consoles.

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We see that number is true and 55 and that's the number.

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So we're not seeing the bigger than 50.

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Let's try some of the other falsies.

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So set it to zero and we see that check number is not true.

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So it's not there.

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It's not true.

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And you can also add in an explanation, Mark, so that will negate that.

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So instead of being false, that will toggle it to be true.

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So it's a one little quick trick that you can do as well.

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So all of the ones that are null and undefined, it's always going to come back.

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And we're not seeing this message being output.

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So it's only until we have a value that's held in here.

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So even if we have a value of 500, you're going to see that that value is being output.

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And here's again, that type conversion where JavaScript is taking this string and it's saying, is

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that string larger than 50?

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And it's checking to see if it's trying to convert that string.

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So first thing it tries to do when it sees a string and tries to convert it in a number and if it works,

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then it's going to output it.

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But if you have something like test, then of course you can't check to see if test is larger than 50.

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So that's not going to come back and that's going to come back as a not a number.

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And remember, not a numbers are falsies.

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So that's why we're not seeing that output of that statement.

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And then lastly, for some bonus marks, check to see if the value of let's turn it back to five.

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So it's a string value of five.

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So we're going to check if check number is equal to five.

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And so what do you think is going to happen here?

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Do you think it's going to output that and we'll just put.

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Yes, there.

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So do you think yes.

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It's going to be output in the console or not?

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And remember that the three equal signs are different than the two equal signs because that's also looking

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for the data type.

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So when we have two equal signs, we see us.

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When we have three equal signs, we don't see us because that's not going to be a true statement.

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So try this out, have some fun with that experiment.

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And coming up next, more advanced with our conditions.