React Web Development: A Guide to Develop Progressive Web Applications

React Web Development: A Guide to Develop Progressive Web Applications

Outperform your competition with progressive web development and React.

Progressive web applications (PWAs) quickly gained popularity because they are web performance applications based on fast performance, streamlined to provide a mobile app-like experience. PWAs are built using HTML, CSS, and JavaScript to create a level of availability and performance equivalent to that of native mobile applications. They respond quickly, consume less data, store more space, and support push notifications and offline use in the browser.

Building a progressive web application has now become the web development trend that every business wants to follow. Significant players like Twitter and Flipboard have recently rolled out their progressive web apps to provide a mobile experience for users, without requiring them to install the app. In this article, you will learn how to build a progressive web application using React. Let's get started.

Step One — Set up the React Application

First, create a React application with create-react-app. To do so, you need to run the following commands:

  • npm install -g create-react-app
  • create-react-app pwa-app

Now, install React Router:

You need to replace the content of src / App.js using the code below to get a basic template with navigation.

import React, { Component } from 'react';
import { Router, browserHistory, Route, Link } from 'react-router';
import './App.css';

const NavBar = () => (
<div className="navbar">
<Link to="/">Feed</Link>
<Link to="/profile">Profile</Link>
</div>
);

const Template = ({ title }) => (
<div>
<NavBar />
<p className="page-info">
This is the {title} page.
</p>
</div>
);

const Feed = (props) => (
<Template title="Feed"/>
);

const Profile = (props) => (
<Template title="Profile"/>
);

class App extends Component {
render() {
return (
<Router history={browserHistory}>
<Route path="/" component={Feed}/>
<Route path="/profile" component={Profile}/>
</Router>
);
}
}
export default App;

Now, you'll have to update the default styles by replacing your src/App.css with the styles below to make your application look clean.

.navbar {
background-color: #01C8E5;
text-align: center;
}

.navbar a {
display: inline-block;
padding: 10px;
color: #fff;
text-decoration: none;
}

.page-info {
text-align: center;
font-weight: bold;
}

Then, run npm start to test the application in the browser. It is basically an application with two routes. Now, you will convert it to PWA.

Step Two — Lighthouse Setting and Auditing

Lighthouse is an automated open-source tool for testing applications against PWA checklists. It facilitates audits for accessibility, performance, and more.

Check your application with Lighthouse. Click the Lighthouse icon from the top right corner in Chrome and then click the "Create Report" button. The generated report will look like this:

Creating a report to test your PWA with Lighthouse

Fix all failed audits.

Step 3 — Sign Up for a Service Staff

Service employees are proxy servers that connect the application and the network. With Service Worker, you will have to block network requests and save cached files. It allows your application to work even with an unavailable system.

Create an empty worker.js file in your application's general directory and add the following code to that file.

// Flag for enabling cache in production
var doCache = false;

var CACHE_NAME = 'pwa-app-cache';

// Delete old caches
self.addEventListener('activate', event => {
const currentCachelist = [CACHE_NAME];
event.waitUntil(
caches.keys()
.then(keyList =>
Promise.all(keyList.map(key => {
if (!currentCachelist.includes(key)) {
return caches.delete(key);
}
}))
)
);
});

// This triggers when user starts the app
self.addEventListener('install', function(event) {
if (doCache) {
event.waitUntil(
caches.open(CACHE_NAME)
.then(function(cache) {
fetch('asset-manifest.json')
.then(response => {
response.json();
})
.then(assets => {
// We will cache initial page and the main.js
// We could also cache assets like CSS and images
const urlsToCache = [
'/',
assets['main.js']
];
cache.addAll(urlsToCache);
})
})
);
}
});

// Here we intercept request and serve up the matching files
self.addEventListener('fetch', function(event) {
if (doCache) {
event.respondWith(
caches.match(event.request).then(function(response) {
return response || fetch(event.request);
})
);
}
});

Now, check if the browsers support service staff and then register worker.js. To do this, you need to add the following script to the file public/index.html (note that shrink-to-fit=no in the viewport meta tag has been deleted).

<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="theme-color" content="#000000">
<link rel="manifest" href="%PUBLIC_URL%/manifest.json">
<link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico">
<title>React App</title>
</head>
<body>
<noscript>
You need to enable JavaScript to run this app.
</noscript>
<div id="root"></div>
<script>
if ('serviceWorker' in navigator) {
window.addEventListener('load', function() {
navigator.serviceWorker.register('worker.js').then(function(registration) {
console.log('Worker registration successful', registration.scope);
}, function(err) {
console.log('Worker registration failed', err);
}).catch(function(err) {
console.log(err);
});
});
} else {
console.log('Service Worker is not supported by browser.');
}
</script>
</body>
</html>

You must restart your application and reload the browser after which you will see the Successful registration of member workers on the developer console. Now, recreate the Lighthouse report.

Step 4 - Improve the Progressive Nature of the Application

Your application will display an original blank div until the JavaScript loads and React hooks the original route. You must make sure your application works without downloading JS and displaying a bit of CSS and HTML before React takes effect. Your updated Index.html will look like this:

<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="theme-color" content="#000000">
<link rel="manifest" href="%PUBLIC_URL%/manifest.json">
<link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico">
<title>React App</title>
<style type="text/css">
body {
margin: 0;
padding: 0;
font-family: sans-serif;
}
.navbar {
background-color: #01C8E5;
text-align: center;
}
.navbar a {
display: inline-block;
padding: 10px;
color: #fff;
text-decoration: none;
}
.page-info {
text-align: center;
font-weight: bold;
}
</style>
</head>
<body>
<noscript>
You need to enable JavaScript to run this app.
</noscript>
<div id="root">
<div class="navbar">
<a href="/">Feed</a>
</div>
<p class="page-info">
Loading an awesome app...
</p>
</div>
<script>
if ('serviceWorker' in navigator) {
window.addEventListener('load', function() {
navigator.serviceWorker.register('worker.js').then(function(registration) {
console.log('Worker registration successful', registration.scope);
}, function(err) {
console.log('Worker registration failed', err);
}).catch(function(err) {
console.log(err);
});
});
} else {
console.log('Service Worker is not supported by browser.');
}
</script>
</body>
</html>

Now, use Lighthouse to retest your application, and you'll see an improvement in the performance of the application.

Step 5 - Add the Splash Icon

You are required to add a 512x512 icon to display on the screen. To do so, you will have to update the manifest.json file and add the t0 icon to the public directory.

{
"short_name": "React App",
"name": "Create React App Sample",
"icons": [
{
"src": "icon-192x192.png",
"sizes": "192x192",
"type": "image/png"
},
{
"src": "icon-512x512.png",
"sizes": "512x512",
"type": "image/png"
}
],
"start_url": "/",
"display": "standalone",
"theme_color": "#000000",
"background_color": "#ffffff"
}

Also, use the following meta tags to allow the browser to determine that your application is a PWA.

<!-- Tell the browser it's a PWA -->
<meta name="mobile-web-app-capable" content="yes">
<!-- Tell iOS it's a PWA -->
<meta name="apple-mobile-web-app-capable" content="yes">
Step 6 — Implement PWA

Now, only HTTPS is missing, and the cache can be fixed after you deploy the application. Update the doCache flag with true in the worker.js file. Create a new project in the firebase dashboard and name it "Pwa Application." Then, run the following command in the project directory:

npm install -g firebase-tools
firebase login
firebase init

Your Firebase.json will look like this:

{
"hosting": {
"public": "build",
"rewrites": [
{
"source": "**",
"destination": "/index.html"
}
]
}
}

After initializing, building and deploying your application.

  • npm run build
  • firebase deploy

You will see results after you test the application using Lighthouse on the deployed URL.

Final product with Lighthouse

Finally, you have created your first progressive web application with React.js!

Originally published by Manoj Kumar Bardhan at  dzone.com

=======================================================

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JavaScript developers should you be using Web Workers?

JavaScript developers should you be using Web Workers?

Do you think JavaScript developers should be making more use of Web Workers to shift execution off of the main thread?

Originally published by David Gilbertson at https://medium.com

So, Web Workers. Those wonderful little critters that allow us to execute JavaScript off the main thread.

Also known as “no, you’re thinking of Service Workers”.

Photo by Caleb Jones on Unsplash

Before I get into the meat of the article, please sit for a lesson in how computers work:

Understood? Good.

For the red/green colourblind, let me explain. While a CPU is doing one thing, it can’t be doing another thing, which means you can’t sort a big array while a user scrolls the screen.

This is bad, if you have a big array and users with fingers.

Enter, Web Workers. These split open the atomic concept of a ‘CPU’ and allow us to think in terms of threads. We can use one thread to handle user-facing work like touch events and rendering the UI, and different threads to carry out all other work.

Check that out, the main thread is green the whole way through, ready to receive and respond to the gentle caress of a user.

You’re excited (I can tell), if we only have UI code on the main thread and all other code can go in a worker, things are going to be amazing (said the way Oprah would say it).

But cool your jets for just a moment, because websites are mostly about the UI — it’s why we have screens. And a lot of a user’s interactions with your site will be tapping on the screen, waiting for a response, reading, tapping, looking, reading, and so on.

So we can’t just say “here’s some JS that takes 20ms to run, chuck it on a thread”, we must think about where that execution time exists in the user’s world of tap, read, look, read, tap…

I like to boil this down to one specific question:

Is the user waiting anyway?

Imagine we have created some sort of git-repository-hosting website that shows all sorts of things about a repository. We have a cool feature called ‘issues’. A user can even click an ‘issues’ tab in our website to see a list of all issues relating to the repository. Groundbreaking!

When our users click this issues tab, the site is going to fetch the issue data, process it in some way — perhaps sort, or format dates, or work out which icon to show — then render the UI.

Inside the user’s computer, that’ll look exactly like this.

Look at that processing stage, locking up the main thread even though it has nothing to do with the UI! That’s terrible, in theory.

But think about what the human is actually doing at this point. They’re waiting for the common trio of network/process/render; just sittin’ around with less to do than the Bolivian Navy.

Because we care about our users, we show a loading indicator to let them know we’ve received their request and are working on it — putting the human in a ‘waiting’ state. Let’s add that to the diagram.

Now that we have a human in the picture, we can mix in a Web Worker and think about the impact it will have on their life:

Hmmm.

First thing to note is that we’re not doing anything in parallel. We need the data from the network before we process it, and we need to process the data before we can render the UI. The elapsed time doesn’t change.

(BTW, the time involved in moving data to a Web Worker and back is negligible: 1ms per 100 KB is a decent rule of thumb.)

So we can move work off the main thread and have a page that is responsive during that time, but to what end? If our user is sitting there looking at a spinner for 600ms, have we enriched their experience by having a responsive screen for the middle third?

No.

I’ve fudged these diagrams a little bit to make them the gorgeous specimens of graphic design that they are, but they’re not really to scale.

When responding to a user request, you’ll find that the network and DOM-manipulating part of any given task take much, much longer than the pure-JS data processing part.

I saw an article recently making the case that updating a Redux store was a good candidate for Web Workers because it’s not UI work (and non-UI work doesn’t belong on the main thread).

Chucking the data processing over to a worker thread sounds sensible, but the idea struck me as a little, umm, academic.

First, let’s split instances of ‘updating a store’ into two categories:

  1. Updating a store in response to a user interaction, then updating the UI in response to the data change
  2. Not that first one

If the first scenario, a user taps a button on the screen — perhaps to change the sort order of a list. The store updates, and this results in a re-rendering of the DOM (since that’s the point of a store).

Let me just delete one thing from the previous diagram:

In my experience, it is rare that the store-updating step goes beyond a few dozen milliseconds, and is generally followed by ten times that in DOM updating, layout, and paint. If I’ve got a site that’s taking longer than this, I’d be asking questions about why I have so much data in the browser and so much DOM, rather than on which thread I should do my processing.

So the question we’re faced with is the same one from above: the user tapped something on the screen, we’re going to work on that request for hopefully less than a second, why would we want to make the screen responsive during that time?

OK what about the second scenario, where a store update isn’t in response to a user interaction? Performing an auto-save, for example — there’s nothing more annoying than an app becoming unresponsive doing something you didn’t ask it to do.

Actually there’s heaps of things more annoying than that. Teens, for example.

Anyhoo, if you’re doing an auto-save and taking 100ms to process data client-side before sending it off to a server, then you should absolutely use a Web Worker.

In fact, any ‘background’ task that the user hasn’t asked for, or isn’t waiting for, is a good candidate for moving to a Web Worker.

The matter of value

Complexity is expensive, and implementing Web Workers ain’t cheap.

If you’re using a bundler — and you are — you’ll have a lot of reading to do, and probably npm packages to install. If you’ve got a create-react-app app, prepare to eject (and put aside two days twice a year to update 30 different packages when the next version of Babel/Redux/React/ESLint comes out).

Also, if you want to share anything fancier than plain data between a worker and the main thread you’ve got some more reading to do (comlink is your friend).

What I’m getting at is this: if the benefit is real, but minimal, then you’ve gotta ask if there’s something else you could spend a day or two on with a greater benefit to your users.

This thinking is true of everything, of course, but I’ve found that Web Workers have a particularly poor benefit-to-effort ratio.

Hey David, why you hate Web Workers so bad?

Good question.

This is a doweling jig:

I own a doweling jig. I love my doweling jig. If I need to drill a hole into the end of a piece of wood and ensure that it’s perfectly perpendicular to the surface, I use my doweling jig.

But I don’t use it to eat breakfast. For that I use a spoon.

Four years ago I was working on some fancy animations. They looked slick on a fast device, but janky on a slow one. So I wrote fireball-js, which executes a rudimentary performance benchmark on the user’s device and returns a score, allowing me to run my animations only on devices that would render them smoothly.

Where’s the best spot to run some CPU intensive code that the user didn’t request? On a different thread, of course. A Web Worker was the correct tool for the job.

Fast forward to 2019 and you’ll find me writing a routing algorithm for a mapping application. This requires parsing a big fat GeoJSON map into a collection of nodes and edges, to be used when a user asks for directions. The processing isn’t in response to a user request and the user isn’t waiting on it. And so, a Web Worker is the correct tool for the job.

It was only when doing this that it dawned on me: in the intervening quartet of years, I have seen exactly zero other instances where Web Workers would have improved the user experience.

Contrast this with a recent resurgence in Web Worker wonderment, and combine that contrast with the fact that I couldn’t think of anything else to write about, then concatenate that combined contrast with my contrarian character and you’ve got yourself a blog post telling you that maybe Web Workers are a teeny-tiny bit overhyped.

Thanks for reading

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Further reading

An Introduction to Web Workers

JavaScript Web Workers: A Beginner’s Guide

Using Web Workers to Real-time Processing

How to use Web Workers in Angular app

Using Web Workers with Angular CLI


Why ReactJS is better for Web Application Development?

Why ReactJS is better for Web Application Development?

Web Application Development is the point of contact for a business in today's digital era. It is important to choose the right platform for Web Application Development to build a high end Web

Web Application Development is essential for a business in today’s digital era. Finding the right platform for Web Application Development is important for building an effective Web Application that can enhance the overall customer engagement. Here’s what makes ReactJS a better option for building your next Web Application.