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You have completed Introducing Progressive Web Apps!
You have completed Introducing Progressive Web Apps!
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The application shell architecture is a set of standards that focus on providing a fast-loading experience to users. Using an app shell architecture allows you to give your progressive web apps similar properties of native apps, like instant loading and regular updates.
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Progressive web apps require
a new way of thinking about
0:00
the architecture of your web app.
0:03
When building progressive web apps, it's
recommended to use an application shell or
0:05
apps shell architecture to ensure fast and
0:09
reliable performance, even on
a slow connection or while offline.
0:11
Championed by Google, an app shell
architecture is a set of standards that
0:15
focus on providing a fast loading
experience to users by rendering
0:19
a shell of your application immediately
when a user visits the app,
0:23
before other assets have loaded.
0:27
Using this app shell model allows you to
give your progressive web apps similar
0:28
properties of native apps,
like instant loading and regular updates.
0:32
For instance,
when you first load Flipkart Lite,
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you immediately see the app shell
containing the header UI, navigation and
0:39
loader, before any of
the server data loads.
0:43
App shell architecture separates
the core application infrastructure and
0:45
UI from the data.
0:50
In other words, it separates the parts of
an app that change often, like the data,
0:51
from the parts that don't often change,
like the UI and static assets.
0:55
The application shell
itself is the minimal HTML,
1:00
CSS and JavaScript required to power
the user interface of your app.
1:03
The application shell should load fast,
be cached locally, and
1:08
dynamically display content.
1:12
And since all the UI and infrastructure
is cached using a service worker,
1:14
on subsequent loads your app only needs
to retrieve just the necessary data
1:18
instead of having to
reload the entire app.
1:22
The app shell files are loaded just
once over the network on first visit
1:25
then saved to the device which
results in super fast startup times.
1:29
When designing your app shell,
1:34
you'll first break the app design
down into its core components.
1:35
The components that need to be seen on
screen immediately, like the header,
1:39
title, and navigation, for example.
1:43
As well as other UI components
that are key to the app,
1:45
like a loading indicator and
the layout template for your content.
1:49
Also any supporting resources needed for
the app shell, like images,
1:52
JavaScript, and styles.
1:56
You include those components in your apps
index.html file using regular HTML markup.
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And once you've built your app shell,
you'll need to cache the app shell using
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a service worker so that it's always
available quickly and reliably.
2:07
Now if you're familiar with native app
development, the app shell is similar
2:11
to the bundle of code you'd submit to
an app store when publishing an app.
2:16
It contains just the core components
necessary to get the apps started
2:19
which means it usually
doesn't contain the data.
2:23
Using the application shell model combined
with the core technologies of progressive
2:26
web apps lead to huge wins in both
performance and user experience.
2:30
And keep in mind that the principles and
technologies covered in these videos
2:35
can equally enhance apps built with plain
JavaScript, React, Polymer, Angular or
2:39
any other framework or library you choose
for building your progressive web apps.
2:44
To learn more about application shell
architecture and how to cache an app
2:48
shell with a service worker, check out
the links posted in the teacher's notes.
2:52
So when should you build a progressive
web app over a native app?
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Well there are a few factors
you'll have to consider.
2:59
First, identify your users and
the most important user actions.
3:02
Even though progressive web
apps work in all browsers,
3:07
to deliver the full app like experience,
users will need to be using browsers
3:10
that support modern web technologies,
which isn't always the case.
3:14
If certain browser features that lack
cross-browser support are required for
3:18
important user actions, a native app
might be the better option because it
3:22
will guarantee the same experience for
users.
3:25
Now, the skill set for iOS and
3:28
Android development is very different
than that of a web developer.
3:30
So you'll also take into account whether
you and your team have the resources and
3:34
skills needed to build a progressive
web app using modern web technologies.
3:38
Building and maintaining native apps for
multiple platforms can be expensive and
3:43
they only benefit those
users who install them.
3:47
Plus standing out among
the millions of apps available in
3:50
app stores these days is a tall order.
3:53
Progressive web apps work on
any device with a browser, so
3:55
choosing to build one could reduce costs.
3:58
You'll build a single app
that works on any platform.
4:00
Now for companies with massive user
bases like Instagram, Twitter,
4:03
or Uber, that expect loads of users
to return to their apps frequently,
4:07
a native app is still the way to go.
4:11
Google has been publishing informative
case studies from companies adopting and
4:13
benefiting from converting
to progressive web apps.
4:17
And the results are very encouraging.
4:19
And since Google is leading the charge
in the progressive web app movement,
4:22
they've put together a progressive web app
checklist which breaks down all the things
4:26
you'll need to create the best possible
progressive web app experience.
4:30
They've even built an amazing testing
tool called Lighthouse that automatically
4:34
verifies whether or not your app meets
all the progressive web app requirements.
4:37
You'll find the links to all of
these in the teacher's notes.
4:41
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