What
Is Service Workers?
A Service Worker is a script which runs in the
web browsers and manages to the caching for web applications. This script runs
in the separates and background and don't need any user interactions.
They can query a local cache and deliver a cached response, if it is available in the cached. This makes more reliable and
increase the performance.
A Service Worker is a programmable network proxy
and it intercept all outgoing HTTP requests and use to allowing you to control
how network requests from your page are handled.
The Service Worker is a method that enables
applications to take advantage of persistent data in the background processing,
including hooks to enable bootstrapping of web applications while offline.
What
Is Service Workers in Angular 5+?
Angular 5+ start using service workers and the service
workers are increased the apps reliability and performance without needing to
code against this.
This is the great advantages for angular and Angular’s
service worker is designed for -
ü Improve
the performance regarding the unreliable network connection
ü Minimizing
the risks of serving outdated content
ü It’s
Optimize the end user experience
The
main Design Goal of Angular's Service Worker -
ü Caching
an application
ü When
users refresh applications, they see firstly latest version cached file.
ü The
Updates happen in the background process. Do not interrupt to other process.
ü When
Updates, it’s happen the previous version of the application is served until an
update ready to use
Prerequisites
to Supports Service Workers –
We must have the following Angular and Angular CLI
versions and also our web application must run in a web browser that supports
service workers.
ü Angular
5 or later
ü Angular
CLI 1.6 or later
What
Is Service Worker Life Cycle?
A service worker has a life cycle that is
completely separate from your web apps page.
To install a service worker for our site, we need
to register it, which we do in our pages. To Registering a service worker will
cause the browser to start the service worker install step in the background
process.
Prerequisites to Supports Service workers-
ü Browser
support
ü You
need HTTPS
How
To Register A Service Worker?
To install a service worker you need to kick
start the process by registering it in your page. This tells the browser where
your service worker JavaScript file lives.
You can call below register () every time a page loads without concern; the browser
will figure out if the service worker is already registered or not and handle
it accordingly.
if ('serviceWorker' in navigator) {
window.addEventListener('load', function() {
navigator.serviceWorker.register('/sw.js').then(function(registration) {
// If Registration
was successful
console.log('Success
Registration - ', registration.scope);
},
function(err) {
// If Registration
was failed!
console.log('Failed
Registration - ', err);
});
});
}
This code checks to see if the service worker API
is available, and if it is, the service worker at /sw.js is registered once the
page is loaded.
How
To Install a Service Worker?
After a controlled page kicks off the
registration process, let's shift to the point of view of the service worker
script, which handles the install event.
Example looks like -
self.addEventListener('install', function(event) {
// Perform install steps
});
Inside of our install callback, we need to take
the following steps -
ü Open
a cache
ü Cache
our files
ü Confirm
whether all the required assets are cached or not
Example looks like -
var CACHE_NAME = 'my-site-cache-v1.0';
var urlsToCache = [
'/',
'/styles/site.css',
'/script/site.js'
];
self.addEventListener('install', function(event) {
// Perform install steps
event.waitUntil(
caches.open(CACHE_NAME)
.then(function(cache) {
console.log('Opened cache');
return cache.addAll(urlsToCache);
})
);
});
How
To Cache and return Requests?
After a service worker is installed and the user
navigates to a different page or refreshes, the service worker will begin to
receive fetch events.
self.addEventListener('fetch', function(event) {
event.respondWith(
caches.match(event.request)
.then(function(response) {
// Cache hit -
return response
if (response) {
return response;
}
return fetch(event.request);
})
);
});
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Anil Singh is an author, tech blogger, and software programmer. Book writing, tech blogging is something do extra and Anil love doing it. For more detail, kindly refer to this link..
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