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Selenium in installed, so it’s time to use it to navigate to a webpage. We will look at how we use Chrome dev tools to browse the DOM. As well as, what it looks like when things aren’t working correctly.
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Okay, depending on how long of
a break you just took between now and
0:00
when you watched the previous video,
your workspace might have timed out, so
0:03
I'm gonna make sure that mine is running.
0:07
Okay, it is.
0:09
It would have told me right
here that it was timed out.
0:10
I'm gonna get my REPL back up and
running, so I'm gonna type node.
0:12
And we can use the up arrow to loop
through what we had typed before, so
0:17
let's get our page open again.
0:20
So let's see, we need to start with that,
the const selenium.
0:22
So I'm just pressing up arrow,
then we built our driver.
0:24
Great, and then we got our URL,
set our URL, then we went and got it.
0:29
So let's open that up again,
and so that spit out there.
0:35
Remember that's okay,
that's just to help us debug.
0:37
So here this has been launched,
so let's take a look.
0:41
Let's try and automate this page.
0:46
Let's try to type something
in this box from our code.
0:48
So let's take a look
at in Chrome DevTools.
0:53
Now if these are new to you, there's
more information in the teachers notes.
0:55
They're super hardy tools that you should
be aware of as you work with the web.
0:58
So if you just right-click, so I'm gonna
right-click here and choose Inspect,
1:02
it's gonna open up those tools.
1:07
So you'll notice up top
there's this Elements tab.
1:09
This is where we wanna be, and I'm
gonna drag this down here a little bit.
1:11
There we go, close this console for
right now, here we go.
1:14
So we're looking at the elements tab and
it's got this element highlighted right
1:19
here, which is the input text,
invite someone.
1:22
That's what we're looking for.
1:24
So in order to get a hold of this element,
1:27
we're going to need to have a way to
tell our web driver where to find it.
1:29
Now there's a couple of ways
to do this using WebDriver.
1:33
WebDriver understands XPath queries, which
is a way of navigating a tree of XML.
1:37
Like we have here in our HTML document,
HTML is a subset of XML.
1:42
There's more information
in the teacher's notes, and
1:48
we'll go over this XPath stuff
more throughout the course.
1:50
So don't get too hung up on it right now.
1:52
So the Elements tab here actually has
a little built in tool that we can use to
1:55
test our query.
1:59
I'm gonna make this a little bit bigger.
2:00
So there's a tool, if I press command F or
2:06
control F on Windows,
we can open up a little search box here.
2:09
And this you'll see understands XPath.
2:14
XPath allows you to be very explicit about
the elements that you're looking for.
2:17
So let's build a super explicit path.
2:21
So to represent the root,
you start with a single slash.
2:24
So let's get the root up here.
2:28
So single slash, slash, and
then I'm gonna type HTML.
2:29
And you'll see that when it's founded,
it highlights it.
2:34
So next down our path, we wanna go HTML,
we wanna go to the body, right?
2:37
Because the body is
the next container there.
2:42
So we'll do slash body,
there see it's highlighted.
2:44
We wanna get into what's next.
2:47
We want the div, slash div.
2:49
There's the div highlighted,
there's the header.
2:52
And finally, we want to get to the form.
2:55
[LAUGH] And then finally,
we want to get to the first input there.
3:00
Input, we got it, there we go.
3:04
So now we know that our XPath
query matches our input field.
3:07
So let's go ahead and
let's feed that to our driver.
3:10
So I'm gonna grab this.
3:13
I'm gonna close our tools,
so we've got this page back.
3:16
So the selenium module exports
a handy way to get to these locators.
3:19
Typically, you import it like this.
3:25
So you say, const by equals selenium,
that's the name of the package, .By.
3:27
So I'm gonna import this, so
that we can use it In a shorthand.
3:32
I could just write selenium.By every time.
3:36
So there is a method on
driver called findElement.
3:38
And it takes what is known as a locator.
3:43
And there is a static method off
of the By class named XPath,
3:48
and that will take our query.
3:54
I think I copied it.
3:58
Yeah, cool.
3:59
So I'm gonna paste that there, and so that
returns a locator that findElement needs.
3:59
So I'm gonna go ahead and
I'm gonna store this in a variable.
4:06
So we'll store this in fields.
4:10
So we'll say, field equals,
and that's because
4:12
findElement eventually returns
a web element, so let's store that.
4:16
And we can actually send a series
of key strokes to that element.
4:21
So let's use it, so
we'll say field.sendKeys.
4:25
And we'll say,
found this element with an explicit XPath.
4:31
I'm gonna move this window real quick,
so that we can see it.
4:39
So here it is, I'm gonna click, boom.
4:44
See how it wrote it down there?
4:47
Pretty cool, right?
4:51
So I know that I just said a mouthful,
so let's go over that one more time.
4:52
So our driver here, this driver
has a method named findElement.
4:56
And findElement takes a locator,
and like we said,
5:02
there are lots of ways to
find elements on a web page.
5:06
And one strategy for
locating an element is by using an XPath.
5:11
So By is a helper class from
the selenium package, and it has a nice
5:15
static method called XPath, which
takes our query and returns a locator.
5:21
But you might have noticed that
I said find element eventually
5:27
return the element.
5:30
Now that's because as you know, this web
stuff is usually pretty asynchronous,
5:32
multiple things are running at once.
5:36
In JavaScript, a common way to handle
this asynchronous nature is by using
5:39
a pattern known as promises.
5:43
If these are new to you, have no fear,
there's documentation and
5:45
resources in the teacher's notes.
5:48
Also each of these specific
language web driver implementations
5:50
manage these a little bit differently.
5:53
And the JavaScript version here,
uses something they call managed promises.
5:55
It does a great job of extracting
the worry of promises for you.
6:00
I will point out a couple of places
where you need to be careful with them,
6:04
I promise.
6:07
[LAUGH] See what I did there?
6:08
Pretty cool, that we were able to locate
that field using that XPath, right?
6:10
Now we walked down a very specific path
in the HTML to locate that element.
6:14
This brings up an interesting problem.
6:19
What do you think would
happen if we were to change
6:21
the layout just a little bit on that page?
6:24
Would it still work?
6:26
Well, let's think about it.
6:29
The path to the element, the way we
walk to the element and the change.
6:30
So it wouldn't work anymore.
6:35
So this extremely specific
XPath seems pretty fragile.
6:37
Let's keep that in mind as we look
at other ways of finding elements,
6:42
right after this quick break.
6:45
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