Now that we added this navigation bar,
there is one thing you might notice.
This drop-down here doesn't work.
And if we open the developer tools,
we see that we do have responsive behavior out of the box.
We get this side drawer out of the box,
but clicking that doesn't do anything either.
The reason for that is that
Bootstrap is mainly a CSS package,
it adds those CSS classes,
but for some of the features it wants to offer,
like for example,
for this drop-down menu or this responsive navigation,
it also needs a little bit of Java script code
to open that drop-down or to show this mobile menu.
And therefore, we also should go back
to getting started introduction,
and here we learned that we can also include
some JavaScript code to our site
to use all the Bootstrap features we might need.
So even though the focus is on CSS right now,
we now already see how we can also include
some third-party JavaScript code.
In this case, some code which will work in conjunction
with Bootstrap to add more functionality
besides just the styling.
But we'll see more
and other Java script third-party packages,
which are not related to Bootstrap later.
Here for the moment we can just copy this code,
which includes the entire JavaScript code
Bootstrap might ever need,
and add this to our page.
And here we are instructed to include it
right before the closing body tag.
That is done to ensure that the JavaScript code
is only executed after the entire page code has been parsed.
But of course, in this course,
we learned that we can achieve the same behavior
by adding the defer attribute.
And therefore, here I will add it
before the closing head tag.
Press the auto format short cut,
and actually add this defer attribute to this script tag,
which does now load some external JavaScript file,
a file not stored on our machine,
but instead again, stored on some remote servers
that provide us this prebuilt JavaScript file.
And if we now save this and we go back here,
if I reload this page,
clicking this drop-down now opens the drop-down,
and clicking this menu button here
does open this mobile menu.
So this now works,
and now we also saw how we
can add this JavaScript package.
And now with that,
let's dig back into Bootstrap and let's throw more elements
onto this page to practice
using a third party package in greater detail.