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Let's now actually learn how
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to manipulate classes with JavaScript.
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But the first thing that we have to do is
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to actually react to a click on each of these buttons here.
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So right now, of course, nothing happens.
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So now we need to attach an event handler
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to each of these three buttons.
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We finished the last video
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by learning how we can do something for all
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of these three buttons at the same time.
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Right.
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So for that, we used a for loop which loops
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over this note list,
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which is basically an array holding all of the buttons.
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And so, this "btnsOpenModal",
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at position number "I"
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is the current button element in each iteration.
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And then from there we simply write
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the text content property
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just like on any other element.
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But now, let's take it one step further
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and instead of simply reading the text content property,
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we will call the add event listener method,
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just like we learned in the last project.
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Okay.
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So remember, in order to respond to a click event,
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we will attach an event handler function to the element.
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And event handler and event listener
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are pretty much the same thing.
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So that's why this method is called "event listener."
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So let's say, add event listener,
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and then the name of the event.
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And that is, once more, the click event.
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And then the second argument is the function
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which will contain the code that should be executed
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once the button is clicked.
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So, that will be an anonymous function.
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Remember, so a function without a name,
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and it is of course also a function expression.
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Because it's simply this value here.
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So this function value.
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So just as I explained multiple times already,
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but it's important to keep remembering this stuff
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as we go here through this section.
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And to start, let's simply log
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to the console the text content of the button
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that was clicked.
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Now here was actually a mistake,
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because of course we don't want
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to log to the console this event listener.
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Right.
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It doesn't make any sense.
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Instead we now want to log something
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to the console right here, inside this handler function.
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So that's just "CL" again.
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And then let's just say, "Button clicked."
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Give it a save.
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And now each of these three buttons here
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has their own event handler function attached to it.
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So, button clicked
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and when we click on this one then the same should appear.
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And indeed, now we have two.
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So that's what this two means.
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And as we click here, we get another one,
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and another, and another.
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And so, yeah, this worked.
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So we attached this function here now
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to all of the three buttons.
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And again, because we did it here in the loop,
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while we were looping over this note list,
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which contains all of these three buttons.
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Okay, but now of course, this is not the only thing
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that we want to do.
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Instead, we want to display the model.
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And remember that this model is already in the HTML.
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It is hidden right now because it has the hidden class.
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If it didn't have this hidden class, it would be visible.
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Let me actually show that.
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So I delete it, and if I save it now,
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then you see here is the modal.
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Right.
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Here it is.
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And that's because the hidden class is now gone.
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Basically this is exactly what we will do using JavaScript.
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So, we're moving this class.
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So, what we want to do is take the modal.
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So this element that we selected here previously.
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So we selected it, then stored it into this variable.
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And so now we take that selected element
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and on there we can read the class list property.
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So that's class list.
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And then this class list property itself
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has a couple of methods.
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And the one we're gonna use now is "remove."
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And as I just explained, the class
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that we're gonna remove is the class called "hidden."
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Okay.
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And we can actually also remove multiple classes.
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For that we just have to pass them in with commas,
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like this.
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So here we then specify more classes.
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Just keep in mind that we do not use the dot here.
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So not like this, okay.
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And I'm telling you that because I used to do
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that mistake myself.
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And I remembered that.
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And so, I want you to avoid it.
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So the dot is only for the selector.
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But here we are not anymore selecting anything.
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We're just passing in the name of the class.
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And so all we need is a string with that name.
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Now besides removing classes, we can also add classes
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and we can even check
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if an element contains a certain class or not.
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And we will use all of them in this video and the next one.
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Okay.
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And this should actually already do the trick.
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So when I save this now
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and let's click here, and it worked.
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Great.
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So the hidden class is now gone
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and I can show that to you here.
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Using the inspect
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and then we need to give it some more space back.
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And then you see here the modal class
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that used to be here is no longer there.
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Now we can of course not close it
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because that functionality is not yet there.
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But at least now it is open.
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Now we also have the overlay which is this one,
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which also has the hidden class.
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In order to show that overlay,
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we need to remove the hidden class
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from this element as well.
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So that's easy enough.
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It's just the same thing again.
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So overlay dot class list,
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dot remove,
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and then again, hidden.
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All right.
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And, yeah.
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Beautiful.
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That's really nice.
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So using classes like this is a really, really great
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and handy way of manipulating webpages.
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And in practice adding and removing classes,
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like we just did here,
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is the main way in which we change styles on websites.
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That's because a class basically aggregates many styles
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in just one class.
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Now in this case actually,
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the hidden class only contains this one style here.
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So this would've been the same
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as specifying the display style directly in JavaScript.
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So like we learned in the last project.
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So we could've done also,
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modal, dot style, dot display
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and then send it to block,
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I guess, what was it?
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Yeah, nothing.
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So basically display none means that it's not visible.
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And if we want it to be visible,
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we would set it to display block.
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Okay, so this would do the exact same thing.
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But you can see that it's a bit more of a pain.
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Because then we would have to memorize
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what exactly we have to write here.
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So these property name and the exact value.
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And this is only for one style.
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Imagine that the hidden class actually had 10 properties.
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Then we would have to write all
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of this properties here manually
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and change all their values.
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So that's a lot of work and it's not fun.
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And so instead we can basically aggregate all
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of this properties in one class,
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that we identify here in CSS,
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and then in JavaScript we simply add
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and remove these classes as we need
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or don't need these styles.
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So, usually when you need to manipulate styles on a page,
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then always just export the styles into a class,
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and then use the class just like we did here.
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All right.
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Now what we just did here is for showing the modal window.
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But now let's also add the ability of then hiding it
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by clicking that button.
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So, this button here.
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Okay.
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So right now, as I said,
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it's not possible to close the window,
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unless we reload the whole page.
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So, let's take this button here that we already selected
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and simply add an event listener to that one as well.
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So, button close modal, dot add event listener.
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And again waiting for the click event.
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And then let's specify or function here again.
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Okay.
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So again we are just defining the function here.
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We are not calling it itself.
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It is the JavaScript engin who will call this function
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as soon as the click event happens on exactly this element.
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All right.
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Anyway, here we now want to do the opposite.
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So basically we want to add the class back on.
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So modal dot class list, dot add, this time.
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And so, we add the hidden class back on.
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Which will then hide the modal.
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And the same actually for the overlay.
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So let's just duplicate this line here.
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And change this to overlay
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and yeah, this should already work.
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So that already worked before,
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and now let's check it.
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And yes, it does.
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And it should work for all the three buttons of course.
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And yeah, it does.
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Great.
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So again, this is a very common thing to do.
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We change the appearance of websites
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and of elements like this all the time,
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using this class technique.
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Next up, usually when we click outside of a modal,
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then the modal window also closes.
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So that's pretty common, right.
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So what I mean is, clicking this area here outside,
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should also close this window.
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So basically we want this in a code here
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to also be executed when we click on the modal.
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Or actually on the overlay.
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So let's do that.
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So overlay, dot add,
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event listener,
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click, and now what should I do?
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Well, just to make it work, I can copy this code here.
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But you already know that this is not a good idea, probably.
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But let's just for now see if it works.
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So if we click outside,
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so this is the overlay.
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So as we click it now, then indeed,
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the modal and the overlay are both hidden again.
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Great.
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So this works now.
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But again, we do not want the same code here
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in these two places.
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We want actually the exact same function to be executed,
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no matter if we click the close button
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or if we click the overlay.
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So, how should we do that?
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We can simply export this function
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into a more real named function.
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So let me cut the code from here
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and then I will create a function called, "close modal".
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So const, close modal, equals this function value.
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Okay.
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And so now, this variable here is
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what holds the function value.
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So what I can do now is to here specify
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that close modal function.
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And that's it.
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That's the function right here.
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So this what we have here,
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is exactly the same as this.
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And again, notice that we are not calling the function.
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We are not doing this.
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This would not work at all,
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because it will immediately called a function,
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as soon as JavaScript executes this line.
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But that's not what we want to happen.
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We want to close modal function to be executed
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only as soon as the click event happens
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on the close modal button.
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And now, here we can just do the same thing.
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So again, close modal.
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And that's it, that's so much better
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than what we had before.
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Not only did we make our code more dry.
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But we also made it more readable.
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More expressive, and more declarative.
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So right now, when we read this code here,
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it's a lot easier to understand.
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So, we just read, button close modal,
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add the event listener of close the modal.
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Okay, that makes sense.
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So, just by looking at this line we see
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that when this element is clicked,
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then we want to close the modal.
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The same when the overlay is clicked,
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we want to close the modal.
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All right.
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And so, we know exactly what's gonna happen
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when we read this code.
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And so for that advantage alone,
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let's do the same thing here with this function.
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So the one that opens the modal.
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So let me grab this one,
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just put him up here.
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Can also get rid of this console dot log.
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So let's put the two functions here together.
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So open modal.
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And now this function will be just this.
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Right?
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So I'll just cut it again.
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And paste it here.
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And so now we assigned this function here
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to this open modal variable.
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So once more a nice function expression.
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And now we'll just take that
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and put it here.
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Open modal.
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And of course again, we don't call it.
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We simply declare or we define it here.
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And tell JavaScript, "Hey, whenever a click happens
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"on one of these buttons,
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"then please call this function
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"that we just specified here."
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All right.
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And so, this is our code.
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And it's a lot better.
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So actually we just did some refactoring here.
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And so, restructuring our code
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without changing the functionality.
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And so that means that our code should still work the same.
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And indeed it does.
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We can open and close in two ways
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and we can open it on all of the three buttons.
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Beautiful.
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That's really, really great.
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So to recap, if you want to use the same function
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in multiple event listeners,
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then you need to specify that function
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as a separate function, like this one here.
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And then you can pass that function
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as an argument to multiple "add event listener" methods.
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So just like we did it here.
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Right.
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So that's one of the takeaways of this video.
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And the other one is that we really, in practice,
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use the functionality
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of adding and removing classes all the time
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in order to change the appearance of elements on our page.
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And that's because classes allow us
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to basically aggregate multiple CSS properties in just one,
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like a container.
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So each class functions a bit like a container
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with a lot of properties in it.
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And then here, by adding and removing them,
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we basically can activate and deactivate certain styles,
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all at the same time.
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Okay, so keep that in mind.
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And even better, actually write notes maybe
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with what I'm saying,
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because this is really important stuff.
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So working with classes is something
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that we do all the time.
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And there is a third thing that we do with classes,
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which is to check if a class is actually present
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on a certain element.
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And that's gonna be the topic of the next video,
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along with a learning how to actually deal
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with a key press event.
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So that's yet another really exciting video.
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So, let's now check that out.
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