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All right, so continuing with our third list of exercises, we were just about to start solving number

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three, so this is going to be more or less similar to the first exercise because we can only start

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doing anything after pressing the calculate button.

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So this button has the idea of calculate.

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So let's go back there.

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And let's just get this cold.

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And based it down here, this time, the baton is going to be the calculate button, then we are going

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to start a function.

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And here we are just going to get the two grades and the absences.

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So grade one, let's go back there to see yds.

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So this is grade one, grade two and absences.

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So the idea is grade one.

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Now, let's do the same thing.

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For a grade two.

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And for the.

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Absents.

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Now, before we move ahead, we should test if all of the information have been entered, so let's start

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an if statement and this time we're going to use the OR operator, because if grade one is an empty

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string.

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Or great, too, is an empty string.

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Or.

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Absences is an empty string.

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So if by using the or operator, if one of these tests return true, we're going to enter here.

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So this means that something is wrong so we can just send an alert saying that.

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All fields must be.

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Field, so let's just test this real quick, refreshing the page.

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Now, if I click calculate, I'm seeing the alert, so nothing is going to happen if I feel this one

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and this one and leave the third one blank and click calculate again, nothing is going to happen.

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Only when we type all the information.

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When we fill all the feud's, then something is going to happen.

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So this is what we need to do inside else statement.

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So inside here, the first thing we are going to do is create a variable for the average.

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So average is going to be inside parentheses grade one plus grade two.

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Divided by two.

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And another variable for the present.

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So the presence has to be higher than 70 percent, which means that we're going to get the total number

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of classes, which is 20 subtract by the absences.

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So let's say the person had one absence in this case.

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This is going to return in 19.

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So the person went to the classes 19 times.

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So if we divide this by the total number of classes.

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Then we are going to have the percentage of presence, just one thing to pay attention.

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We should never repeat values like this, because if we are using this for another class, which has

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twenty five or maybe 15 classes, then we are going to look throughout our code and replace this information

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everywhere.

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So to avoid this, we should create a variable for the total.

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Classis, this is in this case, this is 20.

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So now we can just use the variable here and the variable here, so if this changes to a different number,

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we can just change it here and we won't have to be concerned about the rest of the code.

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All right.

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So pretty cool.

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Now, we already have the presence, which should be higher than 70 percent.

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So now let's start doing the tests.

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But now, before moving ahead, remember, we should always test what we're doing while we are doing

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to avoid mistakes, because maybe at the end we just write all the code and if it doesn't work, is

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going to be harder to spot what was the error at the end?

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So now let's just check if the average and presents calculations are correct.

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So let's do console.

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That log for the average.

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And also for the presence.

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So remember, in the beginning of the chorus, I told you that console, that log was our best friend

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because we can use it to test our code while we write it.

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So let's do this.

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Let's refresh the page and let's try eight and six.

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And let's try, I don't know, 10 absences, let's hit calculate, let's go to the council.

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So now we have a very strange result in the console, JavaScript is telling us that the average between

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eight and six is forty three.

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So where does this come from?

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Well, to test this out, let's just go back here.

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And let's.

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Get this statement and run it in the console to see what is going on.

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So if we do this and press enter, we can see that we are getting a string.

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So probably what JavaScript is doing is just at first we are using a plus sign so JavaScript knows what

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to do with strings when we use plus signs.

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So it is just getting eight and concatenating with six.

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So we are getting eighty six.

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But when we divide this eighty six string by two, JavaScript starts to get a bit confused and just

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tries to do what it thinks is the correct thing to do.

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So just convert this string to number and calculate the average.

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So eighty six divided by two is forty three.

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So as you can see, remember when we spoke about type conversions, I told you that you should always

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be careful about this because sometimes we may have unexpected results.

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So in this case we are having a number back.

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But this number is far from being correct, so we should not forget to do this.

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So when we are getting the first grade, we should apply the pass float at first.

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So here we have it and also my apologies, because I forgot to do it in the first exercise, so here

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it worked.

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But this was actually because I was lucky because I should always pay attention and convert these values.

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So here.

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We should have done it like this as well.

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All right, so going down here now, saving this, let's refresh the page first, let's test if this

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one is still working, so.

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Thirty five degrees Celsius, it's ninety five Fahrenheit, this is fine, and now this one, let's

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try the same number.

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So eight and six and 10 absences when we heat calculate now we have the correct values, seven and zero

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point five.

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So now we are safe to move ahead.

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So now we have multiple ways of solving this.

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We can use and and or operators.

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We can do nested conditionals.

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It's really up to you.

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Just try not to write too many lines of code.

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So maybe your solution wasn't the same as mine, but if your solution is working as well, it should

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be fine.

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So the way I'm going to solve this is the following.

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I'm going to start an IF statement and first I'm going to test if the student has failed for both reasons.

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So this means that the.

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Average is.

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Less than six point five.

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And at the same time, the presence.

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It's less than zero point seven.

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So in this case, I know that the student has failed for both reasons.

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So I'm just going to start a variable out here just so I don't have to use the VA keyword all the time.

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So now without.

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It's going to be the student has failed.

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Because of.

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Insufficient grade and too many absences, if you want, you can try to write a better text.

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This is just an example.

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So in this case, I know that the student has failed for both reasons.

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So now I'm just going to start and else if.

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So this time I'm just going to repeat one of these tests so I know this sounds a bit counterintuitive,

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why am I repeating this?

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This is just because we know that if this returns true, so both are true.

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We are going inside here and JavaScript is just going to ignore all the rest of the structure.

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So if we are getting to this point, it means that one of these returned.

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True.

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So if the average is less than six point five, it means that the presence was good because otherwise

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we would have stopped here.

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So in this case, the result.

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It's going to be the student has failed because of insufficient grade.

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So, again, how do we know that it wasn't because of both reasons, because if so, we would have stopped

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here and JavaScript would have ignored all the rest of the structure.

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So now just another else, if that's going to be very similar, but this time we are going to use the

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presence.

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So if we fall here.

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I just forgot the semicolon here and here aswell.

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So if we fall here, it means that the student has failed because of too many absences.

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How do we know it, because if it was because of both reasons, we would have stopped here.

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Then if we don't go inside any of these.

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If statements, we know that the student has been approved, so result.

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It's going to be.

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This student has been approved now the only thing we need to do is just.

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Printing this value inside that element.

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So let's check what is that element?

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This one has the idea of result.

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So now inside it, we are just going to print the result.

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Now, let's make some tests to see if this is working.

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Now, let's try five, five and 10.

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So the student is going to fail for both reasons, let's test this out so now we can see that this is

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working.

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Now, let's do only two absences now.

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It was only because of insufficient grade.

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Now let's try 10 again.

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But this time, two good grades.

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So this time it was only because of the absences of now to good grades and a low number of absences,

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and this time this student has been approved.

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So this is the way I solved it.

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If you did it differently, if you think your way of doing it was more efficient than mine, you can

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just share it in the Q&A section.

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Let's move on.

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There's one thing we didn't do.

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We did not validate this.

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These numbers like.

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Grades from zero to 10, absences from zero to 20, if I try 55 here.

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Our program is just accepting this, but I'm not going to go into this now because this video is getting

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a bit too long, if you want to try to do this validation, you can do it just as an extra challenge

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later.

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And of course, we might talk about data validation.

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So let's just leave it like this for now.

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And now, number four, I honestly spent a bit more time than expected with number three.

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So now let's stop this video.

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And in the next part, we are going to solve number four.

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I'll see you then.