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Create a Reusable Fetch Function
6:31Learn how to simplify your fetch requests by creating a reusable data-fetching function that runs the fetch, returns the response in JSON, and more.
In your projects, you'll often need
to make multiple fetch requests.
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For example, fetch a list of users,
a list of posts by user, and
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comments related to a post.
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Having to repeat the same code to make
a request, handle the response, and
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as you'll learn about later, manage
errors can get tedious and unnecessary.
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So in this video, I'll teach you how
to simplify your fetch requests by
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creating a reusable data fetching
function that runs the fetch, parses and
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returns JSON, and more, all in one place.
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First in app.js,
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I'll create a new function called
fetchData that takes the parameter url.
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This will be a wrapper
function around fetch, so
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it needs to return the fetch method.
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We'll also pass fetch,
the url parameter, and
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I'll chain a then method that
parses the response to JSON.
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So our fetchData function will
return a promise once the data is
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retrieved from the server and
parsed to JSON.
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So now, we can change our two
fetch methods below to fetchData.
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And since the data is already
being returned in JSON,
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we can delete the then methods that
handle and parse the response.
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So good, one less step to worry about.
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Now, in the next video, we're going to
chain more methods to the promise sequence
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in our fetchData function to handle
errors and check the response status.
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So you'll really start to see the benefits
of writing the fetch sequence in one place
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and reusing it anywhere
you need to fetch data.
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Now, there are other approaches you can
use to make your fetch promises modular,
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less repetitive, and easier to maintain.
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And you can have a look at them in
the teacher's notes with this video.
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Next, I'm going to create a fetch
request that uses the breed name images,
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random end point to return a random image
from the selected breed when a user clicks
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the image, or anywhere in the card div,
as you can see here in the final demo.
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And when a user selects a breed,
will also let them know they can click to
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display another random image
of the selected breed.
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So in app.js, I'll create a new
function named fetchBreedImage.
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Inside the function,
I will create a variable named breed, and
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set it to select.value, or
the value of the select element.
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Then, I'll select the image and
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paragraph element that are being
inserted into the card div.
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So first, I will select the image,
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with const image equals
card.querySelector("img").
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And below that, I'll select the paragraph
with card.querySelector("p")
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Now, I'll make a new fetch request
using my handy fetchData function.
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I'll go ahead and copy the endpoint
I need from the API docs, and
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pass it to fetchData.
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Now, instead of passing the URL as
a string, I'll use a template literal
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because I need to insert or interpolate
the value of the breed variable in my URL.
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So I'll replace the value hound with ${},
and
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inside the curly braces,
add the breed variable.
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Again, the fetchData function returns
a promise that will be resolved or
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fulfilled once the data is retrieved
from the server and parsed to JSON.
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So next, I'll chain a then
method to update the image
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to the new image returned by the API.
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So I'll pass then a function that takes
the parsed data, the other parameter data.
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And inside the function, I'll set the
image's source attribute to the returned
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URL via data.message.
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Let's also set the image's alt
text to the value of breed.
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And I'll update the paragraph's
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text content to say Click to view
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more ${breed}s.
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Again, I'm using a template literal and
interpolation here to insert
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the value of the breed variable
into the paragraph text.
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All right,
our fetch breed image function is all set.
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Now, let's wire up the select and
card elements to the new function.
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So under the event listeners comment,
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I'll first call add event
listener on the select menu.
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Passing it, the change event and the
fetchBreedImage function as the callback.
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And when the user clicks
anywhere inside the card,
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we'll also want to load another
random image of the selected breed.
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So I'm also going to call
addEventListener on card,
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this time passing it a click event and
fetchBreedImage as the call back.
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All right, let’s give our code a save and
have a look in the browser.
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I’ll refresh, and now, if I select
the Corgi option from the menu,
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it displays a Corgi image
inside the card div, and
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the text below the image says
Click to view more corgis.
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And if I click anywhere
inside the card div,
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it will load a new random
image of a corgi, perfect.
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