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Using Data and Route Parameters
6:14Web applications need data! Let's get some to work with.
Applications always require data.
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For example, the internet movie database
is only useful because it lets you
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access data about movies,
actors, and directors.
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Using and
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maintaining data is normally handled
by connecting the app to a database.
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To use our flash card application as
an example, a data base would store
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the text for the prompts answers and
hints for each flash cards.
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For applications requiring a log in user
data will also be stored in the database.
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Databases are a big topic though,
too big for this course.
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We can still set up a power
app to use data and
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hook up database later in
the development process.
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In fact developers will always work
this way, creating an app to use some
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local data for development and testing,
then connecting a database later.
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We can add our flash card data in what
sometimes called a flat data file.
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We would put the data that
the database would store
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into the that file and load it.
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Let's create a flat data file to
provide the app splash card data.
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I'll create a folder called data
in the root of my directory,
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and then I'll create a new folder
called flashcardData.json.
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Now, I'll just paste in
some flash card data I've
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included this snipit in
the teacher's notes.
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You can just copy and
paste that into your own file.
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This file contains a JSON
object with the data property.
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The data property refers to an object
with one property called cards.
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Cards is an array of objects that
contain each flashcards' data.
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Feel free to change these questions and
answers in hints, or add more cards.
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Just make sure not to change the JSON
structure or our app won't work.
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Let's pull this data into
our card's routes file.
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On the third line,
I'll require the data file.
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I'll store the JSONs data property
into a constant, named data.
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Then I will go further and
install the card data separately.
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I've separated out the cards because the
cards will be the main data we will want
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to use.
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If you're not familiar with
the ES6 syntax here and here.
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This is just the equivalent
of saying cards = data.cards.
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And data, .data.
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It's just more concise this way.
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You can also include
JSON directly in Node.
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It reads the text file and then parses the
text and coverts it into a JSON object so
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you don't have to call json.parse.
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Let's connect the template to the first
question just to be sure it's
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loading correctly.
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In the objects we're
passing in to the template.
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I'll point the prompt property.
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To the first card's question property.
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And the hint to the card's hints.
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Now let's look at it in the browser.
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It's pulling in the data,
and displaying it.
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That's great, but how will we pull up
any card that we want in the browser?
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Let's use a route parameter for that.
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A route parameter is
a variable that a user can put
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right into the URL to point
to a particular resource.
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For our current URL,
we want to place a number at the end
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indicating which card to display.
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Our first one would server like this.
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Our second one would be 1 and so on.
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Right now if i hit Enter,
I get a 404 page.
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Let's set up our parameter route
to take the parameters like this.
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In express,
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we can indicate a route parameter
right here where we declared the URL.
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I can use a colon to tell express the
treat this part of the URL as a variable.
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And if I put :id for
example Express will treat this
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portion of URL as a variable or
a route parameter named id.
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The value for the route parameter
from the URL will be stored in
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the request object params property.
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Let's use the ID parameter to access
the elements in the card's array,
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I'll replace the two zeroes
with references to the value in
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rec.params.id.
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Again, I'm using the id
property on the params
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because that's what I
called it in the URL above.
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Refreshing the URL in the browser is
no longer 404ing and it's working.
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Using URL parameters is a powerful
way to access different resources.
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In the next video we'll take
a look at another way to use a URL
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to post specific data from
a resource called the query string
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