WEBVTT

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<v ->Let's now learn some more JavaScript fundamentals.</v>

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And in this video in particular,

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let's learn about some basic operators.

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And let's start by defining what an operator actually is.

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So an operator basically allows us to transform values

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or combine multiple values

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and really do all kinds of work with values.

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And there are many categories of operators

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like mathematical operators, comparison operators

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logical operators, assignment operators, and many more.

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So in this video,

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let's look at some of these types of operators

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starting with mathematical or arithmetic operators.

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So we already used the plus and minus operators

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but of course we can do all arithmetic operations.

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So we can also do multiplication, division and many more.

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And let's use the minus operator to calculate ages

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based on a person's birth year.

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So let's say ageJonas equals so the current year,

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and I will simply assume that right now it's 2037.

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So that's far in the future

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but let's make this a bit fun and then minus a birth year.

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So let's say 1991.

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Okay.

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And then let's just quickly log it to the console.

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So ageJonas using the auto-completion here.

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And so my age is 46, at least if we are currently in 2037.

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Okay.

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Now let's do the same for someone else.

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So let's say ageSarah

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and notice how we're using

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nicely descriptive variable names here.

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So the age of Jonas and the age of Sarah,

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instead of, for example, saying age one and age two.

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So again, right now it's 2037

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and then let's say Sarah was born in 2018.

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So let's log her age to the console as well.

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And we could now write the same line as this.

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So again, console.log

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but we can actually also log multiple values

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at the same time.

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So for that we just write a comma like this,

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and then the second value.

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And we could do even more by adding more commas.

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So here we could then log something else.

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Give it a save.

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And so here we see now 46 and 19 years.

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Great.

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So that's how we used the minus operator

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to solve a very simple problem

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in this case, simply to calculate an age.

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However, we can actually do better here.

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That's because we have this value here

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that is repeating itself.

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So this year 2037 is appearing both here and here.

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And so that's not good because we are repeating this value.

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So if the year now changes

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then we would have to change it in these both places.

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And we don't like that.

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And so that's why we have the concept of variables.

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So instead of having this value here,

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let's say now and then we assign this value

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to the now variable.

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Okay.

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And notice how I'm always by default using const.

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Okay.

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And that's because I'm not changing

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any of these variables here anywhere in my code.

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Only if I needed to change them, I would switch to that.

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Okay. And now here I can replace this one with now

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and this one and it should work the same and it does.

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Great.

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So that's a very good use case for a variable right there.

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And of course we can use

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all kinds of different math operations.

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So let's say console.log

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and now we could go ahead into

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ageJonas times two,

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so using this asterisk or star,

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or we could also do

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ageJonas and divided by two,

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and notice how these are two different calculations here.

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So one calculation

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and another one,

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or basically another operation.

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And that's because as I mentioned before,

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we can log different values at the same time

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in one console.log.

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So here we are creating one value

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and here we are creating a second value.

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Let's actually divide it by 10

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and then let's also use the exponentiation operator.

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So for example, two to the power of three, okay.

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And here we can use a comment to explain what this means.

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So that's a nice use case.

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So three means two to the power of three,

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which is equal to two times two times two.

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So three times this,

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so this should be eight, right?

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Let's try that.

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And indeed 46, which is Jonas' age, times two is 92,

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then divided by six is 4.6.

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So that's this.

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And then two to the power of three is indeed eight.

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Nice.

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Next, there is another use case

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that we didn't use yet for the plus operator.

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And that's because we can use the plus operator

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to join strings,

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or in other words, to concatenate different strings.

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So let's create two variables,

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firstName equals Jonas

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and lastName equals Schmedtmann.

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And now I can concatenate these two strings using plus.

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So let's log that to the console.

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So firstName plus lastName.

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And let's see.

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And indeed we have now one big string

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with both of the names together.

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So both of the strings that we declared earlier.

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But what if we wanted a space in between there?

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Well, that's not too hard.

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All we need to do is to create another string

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which is just a space

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and then concatenate it here with these two.

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And we can actually do that right here.

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So we want this string,

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firstName which is just Jonas.

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Remember the JavaScript engine

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will simply replace this string with this one.

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Then we create an empty string

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or actually a string with a space

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and then we add that one to lastName.

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So that's gonna be Jonas plus a space plus Schmedtmann.

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Let's see.

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And indeed that's exactly the result that we were after.

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Now there's actually a better way

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of doing this kind of concatenation of strings,

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which is called template strings,

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but let's focus on operators now.

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Okay.

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So this is a very useful one

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that we actually use quite often.

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So another type of operator

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is actually the typeof operator,

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which we already used up here.

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So I'm not gonna do that again.

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So remember here we had the typeof operator

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and that would then give us the type of the value.

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So we already know how that one works.

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So let's move on to the next category,

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which are assignment operators.

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And the most straightforward assignment operator

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is just the equal sign.

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So let's say,

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let x equal 10 plus five.

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And so this equal sign here is actually itself an operator,

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alright?

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So in this line of code, we do actually have two operators.

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We have the plus and then the equal.

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Now in this case, x will be assigned 15

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because the plus operator is executed

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before the assignment operator, okay?

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And that's based on a couple of rules

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about operator proceedings that I'm gonna show you

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in the next video.

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So let me actually show that to you

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that it indeed works as I told you.

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And yeah, so it's 15.

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So 10 plus five is done first

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and then the result of this operation,

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which is 15, will then be assigned to x.

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And so that itself is another operator

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but there are more assignment operators.

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So let me show one to you, which is this one,

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x plus equal 10.

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So we know that at this point after this line

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x is 15, right?

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So let's write that as a comment.

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And then we have this next line.

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So this weird x plus equal.

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So what does plus equal actually mean?

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Well, let's write that again as a comment.

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So what this means is x equal x plus 10.

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So instead of having to write all of this,

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we can simply write x plus equal 10, all right?

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And so x should now be 25

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because this x year from the previous step is 15.

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So here we are basically reassigning the x value.

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That's why I used a let here.

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So again, x at this point here will be 15

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and then 15 plus 10 should be 25.

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And indeed it's now 25.

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So let's write that result here so that we can keep track

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as I show you more operators,

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because as you might imagine,

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there are more operators like this.

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For example, there is x and then times equal four.

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And I hope you can imagine

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that this will mean x is equal x times four

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and this should be in this case 25 times four, so 100.

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Let's check and yes, it works.

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The same operator also exists with divided here,

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but I'm not gonna go into that one.

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So to finish, I will just show you the x plus plus operator.

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And what this will do is

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x equals x plus one.

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So let's see.

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And yes, we have 101.

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And we also have x minus minus.

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So if we do that twice now,

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what do you think will happen here?

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And indeed we get 99.

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So minus minus is basically

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just the opposite of plus plus.

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So this one will decrease the value by one

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and so we end up with 99.

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Okay.

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So let's actually write

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that these are assignment operators

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and these are, let's say math operators.

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And so now let's talk about comparison operators,

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and these are pretty great.

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So basically, we use comparison operators

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to produce Boolean values.

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So let me show you how that works

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and then I'm sure it will make sense

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that the result of a comparison operator

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should be a Boolean.

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So let's say we are trying to figure out

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if ageJonas is greater than ageSarah, right?

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So what could the result of this be

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if we think about this logically?

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So ageJonas can either be greater than Sarah or not.

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And so if it is greater

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then the result of this should be true

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and if it's not,

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then it should just be false.

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So indeed the result of this one is true

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that's because Jonas' age is 46 and Sarah is 19.

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So this is basically like asking the operator,

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"Is the age of Jonas greater than the age of Sarah?"

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And the operator will then essentially reply with

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yes, it is, which means true

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or no, it's not, which means false.

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And this can be very useful later

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when we start taking decisions with our code

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based on conditions like this.

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Okay.

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Now of course there's also the less than,

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so the opposite,

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and also there is greater equal or less than equal.

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So basically we have this one and we have this one

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then we have greater equal and less than or equal.

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So let's see a nice application

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of the greater than equal operator.

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So let's say we wanted to test if Sarah is of full age.

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So that means that she must be at least 18 years old,

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and at least means that she is greater than 18

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or exactly 18.

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And so we can use the appropriate operator for that.

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So greater or equal 18.

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Okay.

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So 18 should already be included

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and that's why we have this equal here.

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So this should be true.

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And yes, it is.

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So if we make her one year younger,

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so let's say she was born in 2019, then her age is 18,

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as you see here,

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and she is still of full eight.

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So it's still true here.

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And that's because we included 18 here

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in the age basically by using this equal sign.

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But now if we made her born in 2020, she would be 17

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and then this should turn out to be false.

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So that's checked out and yes, now it's false.

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Great.

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Now keep in mind that in real development

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we would actually store these results here.

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So for example, the result of this comparison operator

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or this one year,

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we would store these results in variables

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and not just always lock the results to the console.

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Okay.

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But in this case, I just wanted to show

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how all of this works.

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And so we need to console

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because really all we want to do is to see the results

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because we're still learning.

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Okay.

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We could also just do all of this

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right here in the console immediately

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but then we would kind of lose the record

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of what we're learning

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and it would be not so easy to scroll up and down.

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Okay.

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But of course we could just do this, right.

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We could just write ageSarah greater or equal 18,

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and we would still get the same result.

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And this works because the console actually has access

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to all the variables that is running

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in the current browser tab, right.

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So all the variables that we have here

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like firstName, for example,

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they are all right here.

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Can even auto complete them.

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Okay.

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But then again, if we would reload this page now,

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then all we just did would be lost.

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And of course we could also simply as I said,

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just store these results

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if we needed them later in our code.

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so isFullAge and then we could do this.

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And so this variable

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would be the one holding the Boolean value then.

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And actually as you see here in this popup,

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vs code is so smart that it figures out automatically

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that this variable here is gonna be a Boolean

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because of the code that we wrote here

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which of course has a Boolean as a result.

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Okay.

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So now just to finish,

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let's say that we don't want the intermediate age variables

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and do this kind of comparison here,

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all in one go.

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So this here.

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So let me show that to you in the code.

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So again, imagine we have a lot of code

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and we don't want to calculate these ages here separately.

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So we could just do

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now minus 1991,

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and then test if it's greater than now, minus 2020.

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Well, let's actually put it back to 2019

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as we had before, or actually 2018 I think.

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So this now is basically just the same as this year.

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We simply are doing it now all in one step.

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So this code is the same as this as it's highlighted here.

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And this is the same as this one.

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And so this whole line of code

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is essentially the same as doing this.

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Now the big question here is,

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how does JavaScript know

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if it should do the math first

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or if it should do the comparison first, right?

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Because we could think

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that the first thing to do is to calculate this,

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so basically 46

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and then JavaScript could compare that 46 to now right away,

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right?

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That's what would happen

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if the operation would simply proceed from left to right.

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But we will see that it doesn't.

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So we will see that this actually works just fine, right.

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And so JavaScript has some way of knowing

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that it should first do this operation,

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then this one,

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so that it has the two numbers

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and then only at the end,

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once it has the two ages,

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it will compare them with this operator in the middle.

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So how does that work?

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Well, that's what we're gonna talk about, right,

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in the next video.