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Angular Service Workers

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 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

Got a minute? Check out this, Angular 6 Questions | A Complete Guide Book

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
      .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) {
      .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.

By Anil Singh | Rating of this article (*****)

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