How to build Progressive Web Apps (PWAs) with Angular

How to build Progressive Web Apps (PWAs) with Angular

In this tutorial we’ll build an Angular application, walk through the steps to make it a Progressive Web Applications (PWAs) and then deploy it using Netlify to use the application on a mobile device.

You can use the GitHub repository for reference and code along as we go through the process of building an Angular PWA from scratch.

Build the Angular App

To begin building our Angular application, open your terminal and make a new directory (or choose an existing one) where you want to create the application (app). Then use the following Angular CLI command to create a new Angular app:

ng new angular-pwa

Choose Yes for Angular Routing and CSS for stylesheet format.

We’ll use Angular Material to handle the look, layout, and accessibility of our app. Go into the angular-pwa directory you just created and add Angular Material:

cd angular-pwa
ng add @angular/material

Choose a color theme and answer Yes to add HammerJS and browser animations.

You can take a look at the boilerplate Angular application in your web browser by running:

ng serve -o

The app should load in your default browser and look something like this.

The app we’re building will let users view Technology and JavaScript news headlines. Since users will need to navigate between the two, lets add navigation with Angular Material by running:

ng g @angular/material:material-nav --name navbar

We’ll get our content from the NewsAPI. You’ll need a key to access the api so head on over to the NewsAPI website and sign up as a Developer to get a free key.

Once you have your NewsAPI key, lets create the service provider for our app by running:

ng generate service services/newsapi

This will create a new services subdirectory with boilerplate files inside it. Fire up the code editor of your choice and open the newsapi.service.ts file you just created in angular-pwa/src/app/services/

We want to setup two API endpoints; one for Technology News and another for JavaScript News. The NewsAPI Documentation shows how to format the http endpoints. Here’s what we’ll use:

https://newsapi.org/v2/top-headlines?category=technology&language=en&country=us&apiKey=
https://newsapi.org/v2/everything?q=javascript&sortBy=latest&apiKey=

Now use the code below to edit the newsapi.service.ts file. We’ll add HttpClient and Observable to our imports, and create functions to get the news articles from our API endpoints.

Be sure to put in your NewsAPI key on the line:

_api_key = 'YOUR NEWSAPI KEY GOES HERE'_
import { HttpClient } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { Observable } from 'rxjs';
import { map } from 'rxjs/operators';

@Injectable({
  providedIn: 'root'
})
export class NewsapiService {
  api_key = 'YOUR NEWSAPI KEY GOES HERE';

  constructor(private http: HttpClient) {}

  getArticlesTechnology(): Observable<any> {
    return this.http
      .get(
        'https://newsapi.org/v2/top-headlines?category=technology&language=en&country=us&apiKey=' +
          this.api_key
      )
      .pipe(map((data: any) => data.articles));
  }

  getArticlesJavaScript(): Observable<any> {
    return this.http
      .get(
        'https://newsapi.org/v2/everything?q=javascript&sortBy=latest&apiKey=' +
          this.api_key
      )
      .pipe(map((data: any) => data.articles));
  }
}

To use our new service provider we need to add it and HttpClientModule to our app.module.ts file. Open and edit the app.module.ts file.

import { LayoutModule } from '@angular/cdk/layout';
import { HttpClientModule } from '@angular/common/http';
import { NgModule } from '@angular/core';
import {
  MatButtonModule,
  MatCardModule,
  MatIconModule,
  MatListModule,
  MatSidenavModule,
  MatToolbarModule
} from '@angular/material';
import { BrowserModule } from '@angular/platform-browser';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
import { AppRoutingModule } from './app-routing.module';
import { AppComponent } from './app.component';
import { ArticlesTechnologyComponent } from './articles-technology/articles-technology.component';
import { NavbarComponent } from './navbar/navbar.component';
import { NewsapiService } from './services/newsapi.service';

@NgModule({
  declarations: [AppComponent, NavbarComponent, ArticlesTechnologyComponent],
  imports: [
    BrowserModule,
    AppRoutingModule,
    BrowserAnimationsModule,
    HttpClientModule,
    LayoutModule,
    MatToolbarModule,
    MatCardModule,
    MatButtonModule,
    MatSidenavModule,
    MatIconModule,
    MatListModule
  ],
  providers: [NewsapiService],
  bootstrap: [AppComponent]
})
export class AppModule {}

Now create a new component to display the Technology News by running:

ng g c articles-technology

Head back to your code editor and you’ll see the new articles-technology directory we created — as well as the navbar directory we made earlier.

Open the articles-technology.component.ts file and edit it to add our NewsAPI service and create the array for the Technology News articles.

import { Component } from '@angular/core';
import { Observable } from 'rxjs';
import { NewsapiService } from '../services/newsapi.service';

@Component({
  selector: 'app-articles-technology',
  templateUrl: './articles-technology.component.html',
  styleUrls: ['./articles-technology.component.css']
})
export class ArticlesTechnologyComponent {
  articles$: Observable<any>;

  constructor(private newsapi: NewsapiService) {}

  ngOnInit() {
    // technology news articles
    this.articles$ = this.newsapi.getArticlesTechnology();
  }
}

Next open the articles-technology.component.html file and delete all the boilerplate code that was added when the CLI created it. Edit the file to display the Technology News articles from our service provider.

<mat-card *ngFor="let article of articles$ | async">
  <mat-card-header>
    <mat-card-title class="title">{{ article.title }}</mat-card-title>
    <mat-card-subtitle>{{ article.source.name }}</mat-card-subtitle>
  </mat-card-header>
  <img
    mat-card-image
    class="img-article"
    src="{{ article.urlToImage }}"
    alt=""
  />
  <mat-card-content>
    <p>
      {{ article.description }}
    </p>
  </mat-card-content>
  <mat-card-actions class="action-buttons">
    <a mat-button color="primary" href="{{ article.url }}">
      <mat-icon>description</mat-icon> Full Article
    </a>
  </mat-card-actions>
</mat-card>

Let’s see how that looks. Open the app.component.html file, delete all the boilerplate code and add the articles-technology component:


Save your files and view the app in your browser to see the Technology News being displayed. Now we need to create the JavaScript News component and format our navigation.

In your terminal, create a new component to hold our JavaScript News content:

ng g c articles-javascript

As we did with the articles-technology component files, first we’ll edit the articles-javascript.component.ts:

import { Component, OnInit } from '@angular/core';
import { Observable } from 'rxjs';
import { NewsapiService } from '../services/newsapi.service';

@Component({
  selector: 'app-articles-javascript',
  templateUrl: './articles-javascript.component.html',
  styleUrls: ['./articles-javascript.component.css']
})
export class ArticlesJavascriptComponent implements OnInit {
  JSarticles$: Observable<any>;

  constructor(private newsapi: NewsapiService) {}

  ngOnInit() {
    // javascript news articles
    this.JSarticles$ = this.newsapi.getArticlesJavaScript();
  }
}

And then edit the articles-javascript.component.html file:

<mat-card *ngFor="let article of JSarticles$ | async">
  <mat-card-header>
    <mat-card-title class="title">{{ article.title }}</mat-card-title>
    <mat-card-subtitle>{{ article.source.name }}</mat-card-subtitle>
  </mat-card-header>
  <img
    mat-card-image
    class="img-article"
    src="{{ article.urlToImage }}"
    alt=""
  />
  <mat-card-content>
    <p>
      {{ article.description }}
    </p>
  </mat-card-content>
  <mat-card-actions class="action-buttons">
    <a mat-button color="primary" href="{{ article.url }}">
      <mat-icon>description</mat-icon> Full Article
    </a>
  </mat-card-actions>
</mat-card>

Now that we have our Technology News and JavaScript News components, we’ll add our navigation. First we’ll add routing by editing the app-routing.module.ts file to import our components and construct paths to them.

import { NgModule } from '@angular/core';
import { RouterModule, Routes } from '@angular/router';
import { ArticlesJavascriptComponent } from './articles-javascript/articles-javascript.component';
import { ArticlesTechnologyComponent } from './articles-technology/articles-technology.component';

const routes: Routes = [
  { path: 'articles', component: ArticlesTechnologyComponent },
  { path: 'articles-javascript', component: ArticlesJavascriptComponent }
];

@NgModule({
  declarations: [],
  imports: [RouterModule.forRoot(routes)],
  exports: [RouterModule]
})
export class AppRoutingModule {}

Now we can format the navbar component by editing the navbar.component.html file:

<mat-sidenav-container class="sidenav-container">
  <mat-sidenav
    #drawer
    class="sidenav"
    fixedInViewport="true"
    [attr.role]="(isHandset$ | async) ? 'dialog' : 'navigation'"
    [mode]="(isHandset$ | async) ? 'over' : 'side'"
    [opened]="!(isHandset$ | async)"
  >
    <mat-toolbar>Menu</mat-toolbar>
    <mat-nav-list>
      <a
        mat-list-item
        [routerLink]="['/articles']"
        routerLinkActive="router-link-active"
        >Technology News</a
      >
      <a
        mat-list-item
        [routerLink]="['/articles-javascript']"
        routerLinkActive="router-link-active"
        >JavaScript News</a
      >
    </mat-nav-list>
  </mat-sidenav>
  <mat-sidenav-content>
    <mat-toolbar color="primary">
      <button
        type="button"
        aria-label="Toggle sidenav"
        mat-icon-button
        (click)="drawer.toggle()"
        *ngIf="isHandset$ | async"
      >
        <mat-icon aria-label="Side nav toggle icon">menu</mat-icon>
      </button>
      <span>Angular PWA - powered by NewsAPI.org</span>
    </mat-toolbar>
    <router-outlet></router-outlet>
    <app-articles-technology></app-articles-technology>
  </mat-sidenav-content>
</mat-sidenav-container>

In the navbar.component.html we set our content to be the articles-technology component. So, go back into the app.component.html file and remove the code we added earlier and replace it with our navbar:


Check your browser to see the app is running with navigation to Technology News and JavaScript News.

Build the Progressive Web Apps (PWAs)

Now that we have a functioning app — let’s make it a PWAs! Go to your terminal and run:

ng add @angular/pwa --project angular-pwa

Angular CLI will take care of a few things to setup our Angular application to be a PWAs. It will:

Add the @angular/service-worker package to our app.module.ts file imports:

import{ ServiceWorkerModule } from ‘@angular/service-worker’;
@NgModule({ ..
imports: [ …
ServiceWorkerModule.register(‘ngsw-worker.js’, { enabled: environment.production })
] …

Create two files in the src directory: manifest.json and ngsw-config.json and add manifest.json in the registered assets of our app in the angular.json file.

“assets”: [
“src/favicon.ico”,
“src/assets”,
“src/manifest.json”
]

Update our index.html file with a link to manifest.json and meta tags for theme-color.


If you ever want to change the theme color you’ll need to change it in both the index.html and the manifest.json files.

Alright — lets build our PWA. In your terminal run:

ng build --prod

Notice the new dist directory that was added to our project.

The build created our service workers and everything else our app needs to be a PWA. To see it in action, we’ll need to serve it from an http-server because service workers don’t work with ng serve.

To install http-server globally, go to your terminal and run:

npm i -g http-server

and then launch the PWA by running:

http-server -p 8080 -c-1 dist/angular-pwa

Now go checkout our PWA at: http://127.0.0.1:8080

Open up your browser Dev tools, and in the Network Tab choose Offline then refresh the page. Our PWA is still serving up content thanks to the service worker cache!

Deploy the Progressive Web Apps (PWAs) with Netlify

Okay, we built a PWA with Angular but what’s the point if we don’t get it onto our mobile device? To do that, let’s use Netlify.

Netlify is a cloud based hosting company that quickly deploys static websites with continuous deployment from a git repository.

The first thing to do is make a repository from your code on GitHub, GitLab, or BitBucket. Then head over to Netlify and sign up using your git service. They have a Free tier for experiments like this tutorial.

Login and click on New site from Git button.

Add your repository and enter ng build --prod as the build command and dist/angular-pwa as the publish directory — then click the Deploy site button.

When the deploy is finished, you’ll get a URL you can open on your smartphone to view your PWA. Save it to your home screen to save an icon to your creation.

I hope you found building a PWA with Angular with this tutorial as useful and fun as I did.

Thanks for reading

If you liked this post, share it with all of your programming buddies!

Follow us on Facebook | Twitter

Further reading

The Web Developer Bootcamp

Angular 8 (formerly Angular 2) - The Complete Guide

The Complete JavaScript Course 2019: Build Real Projects!

Modern React with Redux [2019 Update]

Vue JS 2 - The Complete Guide (incl. Vue Router & Vuex)

Build Responsive Real World Websites with HTML5 and CSS3

Build a Progressive Web App In VueJs

Build Progressive Web Apps with React

The State of Progressive Web Apps - The State of the Web

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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

If you liked this post, share it with all of your programming buddies!

Follow us on Facebook | Twitter

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


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