What Is Service Workers?
Stayed Informed - Angular 6 Questions | A Complete Guide Book
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 doesn'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 increases
the performance.
A Service Worker is a programmable network proxy
and it intercept all outgoing HTTP requests and uses 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?
Angular 5+ start using service workers and the
service workers are increased the reliability and performance of the app
without needing to code against this.
This is the great advantages of angular and
Angular’s service worker is designed for -
1. Improve
the performance regarding the unreliable network connection
2. Minimizing
the risks of serving out-dated content
3. It’s
Optimize the end user experience
The
main design goal of Angular's Service Worker -
1. Caching
an application
2. When
users refresh applications, they see firstly latest version cached file.
3. The
Updates happen in the background process. Do not interrupt other processes.
4. When
Updates, it happened 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.
1. Angular
5 or later
2. 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 on 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-
1. Browser
support
2. You
need HTTPS
How to Register a Service Worker?
To install a service worker you need to kick-start
the process by registering it on 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.
The following example looks like this.
self.addEventListener('install',
function(event)
{
// To perform install steps
});
Inside of our install callback, we need to take
the following steps -
1. Open
a cache
2. Cache
our files
3. Confirm
whether all the required assets are cached or not
The following example looks like this.
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.
The following example looks like this.
self.addEventListener('fetch',
function(event)
{
event.respondWith(
caches.match(event.request)
.then(function(response)
{
//Cache return
response
if
(response) {
return
response;
}
return
fetch(event.request);
})
);
});
What Is Angular Language Service?
The Language Service is a way to find the typing
hints, autocompletion, errors, and navigations inside your templates. It can be
an external HTML file or embedded decorators in a string.
Let’s understand the following points -
1. Autocompletion
- It provides you a language hint for speed up the code of your app.
2. Error checking
- It provides you a warning message on your code mistake.
3. Navigation
- It allows you to hover to see where a component, directives, modules, and
then click or press F12 to go directly to its definition.