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4 years ago

Angular 8 Tutorial: Learn to Build Angular 8 Application from Scratch

Angular is one of the three most popular frameworks for front-end development, alongside with React and Vue.js. The latest version is Angular 8 which was released on May 28, 2019, with many new features and enhancements to both the command-line interface and the framework itself resulting in performance-boosting and smaller production bundles. One interesting feature is the ng deploy command which allows developers to quickly build and deploy their Angular app to popular hosting providers such as Firebase or GitHub.

In this tutorial, we’ll take you, step by step, in a journey to build an example Angular application from scratch that uses many of Angular APIs such as HttpClient, and Material Design.

We’ll learn how to mock a REST API server that uses fake data from a JSON file and how to consume the REST API from our Angular 8 application using Httplient

We’ll learn how to handle HTTP errors using the RxJS throwError() and catchError() operators, how to retry failed HTTP requests in poor network conditions and cancel pending requests using the RxJS retry() and takeUntil() operators,

We’ll also learn how to create and make use of Angular components and services, how to set up routing and Angular Material in our project and create a professional-looking UI with Material Design components.

At the last step, we’ll learn how to deploy the application to Firebase using the ng deploy command available in Angular 8.3+.

You’ll learn by example:

  • How to quickly mock a REST API with real-world features, such as pagination, that you can consume from your app before you can switch to a real backend when it’s ready.
  • How to set up Angular CLI,
  • How to initialize your Angular 8 project,
  • How to set up Angular Material,
  • How to add Angular components, and add routing,
  • How to generate and use Angular services,
  • How to consume REST APIs with Angular HttpClient,
  • How to build and deploy your Angular application to Firebase.

This tutorial is divided into the following steps:

  • Step 1 — Installing Angular CLI 8
  • Step 2 — Creating your Angular 8 Project
  • Step 3 — Adding Angular HttpClient
  • Step 4 — Creating Components
  • Step 5 — Adding Routing
  • Step 6 — Building the UI with Angular Material Components
  • Step 7 — Mocking a REST API
  • Step 8 — Consuming the REST API with Angular HttpClient
  • Step 9 — Handling HTTP Errors
  • Step 10 — Adding Pagination
  • Step 11 — Building and Deploying your Angular Application to Firebase

Now, let’s get started with the prerequisites!

Prerequisites

If you want to follow this tutorial, you’ll need to have:

  • Prior knowledge of TypeScript.
  • A development machine with Node 8.9+, and NPM 5.5.1+ installed. Node is required by the Angular CLI. You can head to the official website and grab the binaries for your system. You can also use NVM — Node Version Manager — a POSIX-compliant bash script to install and manage multiple Node.js versions in your machine.

If you are ready, let’s learn by example how to build an Angular 8 application that consumes a REST API using HttpClient and implement real-world features like error handling, and retrying failed HTTP requests.

Step 1 — Installing Angular CLI 8

Let’s start with the first step, where we’ll install the latest version of Angular CLI.

Angular CLI is the official tool for initializing and working with Angular projects. Head to a new terminal and execute the following command:

$ npm install -g @angular/cli

When writing this tutorial, angular/cli v8.3.2 is installed on our system.

That’s it, you are ready for the second step!

Step 2 — Creating your Angular 8 Project

In this step, we’ll use Angular CLI to initialize our Angular project.

Go to your terminal and execute these commands:

$ cd ~  
$ ng new angular-example

The CLI will prompt you if Would you like to add Angular routing? Say Yes and Which stylesheet format would you like to use? Choose CSS.

Angular CLI will generate the required files and folders, install the packages from npm and even automatically set up routing in our project.

Now, go to your project’s root folder and run the local development server using these commands:

$ cd angular-example  
$ ng serve

Your Angular web application will be available from the [http://localhost:4200/](http://localhost:4200/) address.

Open a web browser and go to the http://localhost:4200/ address, you should see this beautiful page (Starting with Angular 8.3+):

You need to let the development server running and open a new terminal for the next steps.

You are now ready for the third step!

Step 3 — Adding Angular HttpClient

In this step, we’ll add HttpClient to our example project.

Open the src/app/app.module.ts file, and the following changes:

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';

import { AppRoutingModule } from './app-routing.module';
import { AppComponent } from './app.component';
import { HttpClientModule } from '@angular/common/http';

@NgModule({
  declarations: [
    AppComponent,
  ],
  imports: [
    BrowserModule,
    AppRoutingModule,
    HttpClientModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

We simply imported HttpClientModule and included it in the imports array.

That’s all, we can use the HttpClient service in our Angular project to consume our REST API.

You are ready for the fifth step!

Step 4 — Creating UI Components

Angular apps are made up of components. In this step, we’ll learn how to create a couple of Angular components that compose our UI.

Open a new terminal and run the following command:

$ cd ~/angular-example  
$ ng g component home

You’ll get the following output in your terminal:

CREATE src/app/home/home.component.html (19 bytes)  
CREATE src/app/home/home.component.spec.ts (614 bytes)  
CREATE src/app/home/home.component.ts (261 bytes)  
CREATE src/app/home/home.component.css (0 bytes)  
UPDATE src/app/app.module.ts (467 bytes)

We have four files, all required by our component.

Next, generate the about component:

$ ng g component about

Next, open the src/app/about/about.component.html file and add the following code:

<p style="padding: 15px;"> This is the about page that describes your app</p>

You are ready for the sixth step!

Step 5 — Adding Routing

In this step, we’ll learn to add routing to our example.

Go to the src/app/app-routing.module.ts file, and add the following routes:

import { NgModule } from '@angular/core';
import { Routes, RouterModule } from '@angular/router';
import { HomeComponent } from './home/home.component';
import { AboutComponent } from './about/about.component';

const routes: Routes = [
  { path: '', redirectTo: 'home', pathMatch: 'full'},
  { path: 'home', component: HomeComponent },
  { path: 'about', component: AboutComponent },
];

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

We imported the Angular components, and we declared three routes.

The first route is for redirecting the empty path to the home component, so we’ll be automatically redirected to the home page when we first visit the app.

That’s it, now that you have added routing, you are ready for the next step!

Step 6 — Adding Angular Material

In this tutorial step, we’ll learn to set up Angular Material in our project and build our application UI using Material components.

Go to your terminal, and run this command from the root of your project:

$ ng add @angular/material

You’ll be prompted for the theme, let’s pick Indigo/Pink.

For the other questions, Set up HammerJS for gesture recognition? and Set up browser animations for Angular Material? Press Enter to use the default answers.

Open the src/app/app.module.ts file and add the following imports:

import { MatToolbarModule,
  MatIconModule,
  MatCardModule,
  MatButtonModule,
  MatProgressSpinnerModule } from '@angular/material';

We imported the modules for these Material Design components:

  • MatToolbar that provides a container for headers, titles, or actions.
  • MatCard that provides a content container for text, photos, and actions in the context of a single subject.
  • MatButton that provides a native <button> or <a> element enhanced with Material Design styling and ink ripples.
  • MatProgressSpinner that provides a circular indicator of progress and activity.

Next, add these modules to the imports array:

@NgModule({
  declarations: [
    AppComponent,
    HomeComponent,
    AboutComponent
  ],
  imports: [
    BrowserModule,
    AppRoutingModule,
    HttpClientModule,
    BrowserAnimationsModule,
    MatToolbarModule,
    MatIconModule,
    MatButtonModule,
    MatCardModule,
    MatProgressSpinnerModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

Next, open the src/app/app.component.html file and update it as follows:

<mat-toolbar color="primary">  
<h1>  
My Angular Store  
</h1>  
<button mat-button routerLink="/">Home</button>  
<button mat-button routerLink="/about">About</button></mat-toolbar><router-outlet></router-outlet>

We added a top navigation bar with two buttons that take us to the home and about pages.

Step 7 — Mocking a REST API

Go to a new command-line interface and start by installing json-server from npm in your project:

$ cd ~/angular-example
$ npm install --save json-server

Next, create a server folder in the root folder of your Angular project:

$ mkdir server
$ cd server

In the server folder, create a database.json file and add the following JSON object:

{
    "products": []
}

This JSON file will act as a database for your REST API server. You can simply add some data to be served by your REST API or use Faker.js for automatically generating massive amounts of realistic fake data.

Go back to your command-line, navigate back from the server folder, and install Faker.js from npm using the following command:

$ cd ..
$ npm install faker --save

At the time of creating this example, faker v4.1.0 will be installed.

Now, create a generate.js file and add the following code:

var faker = require('faker');

var database = { products: []};

for (var i = 1; i<= 300; i++) {
  database.products.push({
    id: i,
    name: faker.commerce.productName(),
    description: faker.lorem.sentences(),
    price: faker.commerce.price(),
    imageUrl: "https://source.unsplash.com/1600x900/?product",
    quantity: faker.random.number()
  });
}

console.log(JSON.stringify(database));

We first imported faker, next we defined an object with one empty array for products. Next, we entered a for loop to create 300 fake entries using faker methods like faker.commerce.productName() for generating product names. Check all the available methods. Finally we converted the database object to a string and log it to standard output.

Next, add the generate and server scripts to the package.json file:

  "scripts": {
    "ng": "ng",
    "start": "ng serve",
    "build": "ng build",
    "test": "ng test",
    "lint": "ng lint",
    "e2e": "ng e2e",
    "generate": "node ./server/generate.js > ./server/database.json",
    "server": "json-server --watch ./server/database.json"
  },

Next, head back to your command-line interface and run the generate script using the following command:

$ npm run generate

Finally, run the REST API server by executing the following command:

$ npm run server

You can now send HTTP requests to the server just like any typical REST API server. Your server will be available from the http://localhost:3000/ address.

These are the API endpoints we’ll be able to use via our JSON REST API server:

  • GET /products for getting the products,
  • GET /products/<id> for getting a single product by id,
  • POST /products for creating a new product,
  • PUT /products/<id> for updating a product by id,
  • PATCH /products/<id> for partially updating a product by id,
  • DELETE /products/<id> for deleting a product by id.

You can use _page and _limit parameters to get paginated data. In the Link header you’ll get first, prev, next and last links.

Leave the JSON REST API server running and open a new command-line interface for typing the commands of the next steps.

Step 8 — Creating a Service for Consuming the REST API with Angular HttpClient

In this step, we’ll learn how to consume our REST API from Angular using HttpClient.

We’ll need to create an Angular service for encapsulating the code that allows us to consume data from our REST API server.

Go to your terminal and run the following command:

$ ng g service api

Next, go to the src/app/api.service.ts file, import and inject HttpClient:

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';

@Injectable({
  providedIn: 'root'
})
export class ApiService {

  private SERVER_URL = "http://localhost:3000";

  constructor(private httpClient: HttpClient) { }
}

We imported and injected the HttpClient service and defined the SERVER_URL variable that contains the address of our REST API server.

Next, define a get() method that sends a GET request to the REST API endpoint:

import { Injectable } from '@angular/core';  
import { HttpClient } from '@angular/common/http';

@Injectable({  
	providedIn: 'root'  
})  
export class ApiService {

	private SERVER_URL = "http://localhost:3000";
	constructor(private httpClient: HttpClient) { }

	public get(){  
		return this.httpClient.get(this.SERVER_URL);  
	}  
}

The method simply invokes the get() method of HttpClient to send GET requests to the REST API server.

Next, we now need to use this service in our home component. Open the src/app/home/home.component.ts file, import and inject the data service as follows:

import { Component, OnInit } from '@angular/core';  
import { ApiService } from '../api.service';

@Component({  
	selector: 'app-home',  
	templateUrl: './home.component.html',  
	styleUrls: ['./home.component.css']  
})  
export class HomeComponent implements OnInit {
	products = [];
	constructor(private apiService: ApiService) { }
	ngOnInit() {
		this.apiService.get().subscribe((data: any[])=>{  
			console.log(data);  
			this.products = data;  
		})  
	}
}

We imported and injected ApiService. Next, we defined a products variable and called the get() method of the service for fetching data from the JSON REST API server.

Next, open the src/app/home/home.component.html file and update it as follows:

<div style="padding: 13px;">
    <mat-spinner *ngIf="products.length === 0"></mat-spinner>

    <mat-card *ngFor="let product of products" style="margin-top:10px;">
        <mat-card-header>
            <mat-card-title>{{product.name}}</mat-card-title>
            <mat-card-subtitle>{{product.price}} $/ {{product.quantity}}
            </mat-card-subtitle>
        </mat-card-header>
        <mat-card-content>
            <p>
                {{product.description}}
            </p>
            <img style="height:100%; width: 100%;" src="{{ product.imageUrl }}" />
        </mat-card-content>
        <mat-card-actions>
      <button mat-button> Buy product</button>
    </mat-card-actions>
    </mat-card>
</div>

We used the <mat-spinner> component for showing a loading spinner when the length of the products array equals zero i.e before no data is received from the REST API server.

Next, we iterated over the products array and used a Material card to display the name, price, quantity, description and image of each product.

This is a screenshot of the home page after JSON data is fetched:

Next, we’ll see how to add error handling to our service.

Step 9 — Adding Error Handling

In this step, we’ll learn to add error handling in our example.

Go to the src/app/api.service.ts file and update it as follows:

import { Injectable } from '@angular/core';
import { HttpClient, HttpErrorResponse } from "@angular/common/http";

import {  throwError } from 'rxjs';
import { retry, catchError } from 'rxjs/operators';

@Injectable({
  providedIn: 'root'
})
export class ApiService {

  private SERVER_URL = "http://localhost:3000/products";

  constructor(private httpClient: HttpClient) { }

  handleError(error: HttpErrorResponse) {
    let errorMessage = 'Unknown error!';
    if (error.error instanceof ErrorEvent) {
      // Client-side errors
      errorMessage = `Error: ${error.error.message}`;
    } else {
      // Server-side errors
      errorMessage = `Error Code: ${error.status}\nMessage: ${error.message}`;
    }
    window.alert(errorMessage);
    return throwError(errorMessage);
  }

  public sendGetRequest(){
    return this.httpClient.get(this.SERVER_URL).pipe(catchError(this.handleError));
  }
}

This is a screenshot of an example error on the browser console:

In the next step, we’ll see how to add pagination to our application

Step 10 — Adding Pagination

In this step, we’ll learn to add support for data pagination using the Link header of the HTTP response received from the REST API server.

By default, HttpClient provides only the response body but in our app we need to parse the Link header for extracting pagination links so we need to instructHttpClient to give us the full HttpResponse using the observe option.

The Link header in HTTP allows the server to point an interested client to another resource containing metadata about the requested resource.Wikipedia

Open the src/app/data.service.ts file and import the RxJS tap() operator:

import { retry, catchError, tap } from 'rxjs/operators';

Next, add these variables:

public first: string = "";  
public prev: string = "";  
public next: string = "";  
public last: string = "";

Next, add the parseLinkHeader() method that will be used to parse the Link header and populates the previous variables:

  parseLinkHeader(header) {
    if (header.length == 0) {
      return ;
    }

    let parts = header.split(',');
    var links = {};
    parts.forEach( p => {
      let section = p.split(';');
      var url = section[0].replace(/<(.*)>/, '$1').trim();
      var name = section[1].replace(/rel="(.*)"/, '$1').trim();
      links[name] = url;

    });

    this.first  = links["first"];
    this.last   = links["last"];
    this.prev   = links["prev"];
    this.next   = links["next"]; 
  }

Next, update the sendGetRequest() as follows:

  public sendGetRequest(){
    // Add safe, URL encoded _page and _limit parameters 

    return this.httpClient.get(this.SERVER_URL, {  params: new HttpParams({fromString: "_page=1&_limit=20"}), observe: "response"}).pipe(retry(3), catchError(this.handleError), tap(res => {
      console.log(res.headers.get('Link'));
      this.parseLinkHeader(res.headers.get('Link'));
    }));
  }

We added the observe option with the response value in the options parameter of the get() method so we can have the full HTTP response with headers. Next, we use the RxJS tap() operator for parsing the Link header before returning the final Observable.

Since the sendGetRequest() is now returning an Observable with a full HTTP response, we need to update the home component so open the src/app/home/home.component.ts file and import HttpResponse as follows:

import { HttpResponse } from '@angular/common/http';

Next, update the subscribe() method as follows:

ngOnInit(){

this.apiService.sendGetRequest().pipe(takeUntil(this.destroy$)).subscribe((res: HttpResponse<any>)=>{  
	console.log(res);  
	this.products = res.body;  
})  
}

We can now access the data from the body object of the received HTTP response.

Next, go back to the src/app/data.service.ts file and add the following method:

public sendGetRequestToUrl(url: string){  
	return this.httpClient.get(url, { observe: "response"}).pipe(retry(3), 			
	catchError(this.handleError), tap(res => {  
		console.log(res.headers.get('Link'));  
		this.parseLinkHeader(res.headers.get('Link'));
	}));  
}

This method is similar to sendGetRequest() except that it takes the URL to which we need to send an HTTP GET request.

Go back to the src/app/home/home.component.ts file and add define the following methods:

 public firstPage() {
    this.products = [];
    this.apiService.sendGetRequestToUrl(this.apiService.first).pipe(takeUntil(this.destroy$)).subscribe((res: HttpResponse<any>) => {
      console.log(res);
      this.products = res.body;
    })
  }
  public previousPage() {

    if (this.apiService.prev !== undefined && this.apiService.prev !== '') {
      this.products = [];
      this.apiService.sendGetRequestToUrl(this.apiService.prev).pipe(takeUntil(this.destroy$)).subscribe((res: HttpResponse<any>) => {
        console.log(res);
        this.products = res.body;
      })
    }

  }
  public nextPage() {
    if (this.apiService.next !== undefined && this.apiService.next !== '') {
      this.products = [];
      this.apiService.sendGetRequestToUrl(this.apiService.next).pipe(takeUntil(this.destroy$)).subscribe((res: HttpResponse<any>) => {
        console.log(res);
        this.products = res.body;
      })
    }
  }
  public lastPage() {
    this.products = [];
    this.apiService.sendGetRequestToUrl(this.apiService.last).pipe(takeUntil(this.destroy$)).subscribe((res: HttpResponse<any>) => {
      console.log(res);
      this.products = res.body;
    })
  }

Finally, add open the src/app/home/home.component.html file and update the template as follows:

<div style="padding: 13px;">
    <mat-spinner *ngIf="products.length === 0"></mat-spinner>

    <mat-card *ngFor="let product of products" style="margin-top:10px;">
        <mat-card-header>
            <mat-card-title>#{{product.id}} {{product.name}}</mat-card-title>
            <mat-card-subtitle>{{product.price}} $/ {{product.quantity}}
            </mat-card-subtitle>
        </mat-card-header>
        <mat-card-content>
            <p>
                {{product.description}}
            </p>
            <img style="height:100%; width: 100%;" src="{{ product.imageUrl }}" />
        </mat-card-content>
        <mat-card-actions>
      <button mat-button> Buy product</button>
    </mat-card-actions>
    </mat-card>

</div>
<div>
    <button (click) ="firstPage()" mat-button> First</button>
    <button (click) ="previousPage()" mat-button> Previous</button>
    <button (click) ="nextPage()" mat-button> Next</button>
    <button (click) ="lastPage()" mat-button> Last</button>
</div>

This is a screenshot of our application:

Step 11 — Building and Deploying your Angular Application to Firebase

Head back to your command-line interface, make sure you are inside the root folder of your Angular project and run the following command:

$ ng add @angular/fire

This will add the Firebase deployment capability to your project.

As the time of writing this tutorial, @angular/fire v5.2.1 will be installed.

The command will also update the package.json of our project by adding this section:

        "deploy": {
          "builder": "@angular/fire:deploy",
          "options": {}
        }

The CLI will prompt you to Paste authorization code here: and will open your default web browser and ask you to give Firebase CLI permissions to administer your Firebase account.

After you signin with the Google account associated with your Firebase account, you’ll be given the authorization code.

Next, you’ll be prompted: Please select a project: (Use arrow keys or type to search). You should have created a Firebase project before.

The CLI will create the firebase.json and .firebaserc files and update the angular.json file accordingly.

Next, deploy your application to Firebase, using the following command:

$ ng deploy

The command will produce an optimized build of your application (equivalent to the ng deploy --prod command), it will upload the production assets to Firebase hosting.

Conclusion

Throughout this step by step tutorial, you learned to build an Angular application from scratch using the latest Angular 8.3+ version.

You learned to mock a REST API backend for your Angular application with nearly zero-lines of code.

You learned to create a project using Angular CLI, add HttpClient and Angular Material for sending HTTP requests to your mocked REST API backend and styling the UI with Material Design components.

Finally, you learned to deploy your Angular application to Firebase using the ng deploy command available starting from Angular 8.3+.

#angular #web-development #javascript

Angular 8 Tutorial: Learn to Build Angular 8 Application from Scratch
58.55 GEEK