JavaScript Hello World Sample - Angular

Angular is one of the most popular and mature JavaScript frameworks. Check out the following on how to implement Dynamsoft Barcode Reader JavaScript SDK (hereafter called “the library”) into an Angular application.

Official Sample

• Hello World in Angular - Demo
• Hello World in Angular - Source Code

Preparation

Make sure you have node and Angular CLI installed. node 14.16.0 and Angular CLI 11.2.4 are used in the example below.

Create the sample project

Create an out-of-the-box raw Angular application

ng new read-video-angular

CD to the root directory of the application and install the dependencies

npm install dynamsoft-javascript-barcode

Start to implement

Add a file “dbr.js” under “/app/” to configure the library

import DBR from "dynamsoft-javascript-barcode";
DBR.BarcodeReader.engineResourcePath = "https://cdn.jsdelivr.net/npm/dynamsoft-javascript-barcode@8.4.0/dist/";
export default DBR;

Note:

• There are multiple settings available for the configuration, here we only set the engineResourcePath which is essential for the library to get the necessary resources at runtime.

Generate two components

ng generate component barcode-scanner

ng generate component hello-world

Edit the barcode-scanner component

• Open the file .\node_modules\dynamsoft-javascript-barcode\dist\dbr.scanner.html, copy everything and paste in barcode-scanner.component.html.

• In barcode-scanner.component.ts, add code for initializing and destroying the library.

import { Component, OnInit, ElementRef } from '@angular/core';
import DBR from '../dbr';

export class BarcodeScannerComponent implements OnInit {
  bDestroyed = false;
  pScanner = null;
  constructor(private elementRef: ElementRef) { }
  async ngOnInit(): Promise<void> {
    try {
      let scanner = await (this.pScanner = this.pScanner || DBR.BarcodeScanner.createInstance());
      if (this.bDestroyed) {
        scanner.destroy();
        return;
      }
      scanner.setUIElement(this.elementRef.nativeElement);
      await scanner.open();
    } catch (ex) {
      console.error(ex);
    }
  }
  async ngOnDestroy() {
    this.bDestroyed = true;
    if (this.pScanner) {
      (await this.pScanner).destroy();
    }
  }
}

Note:

• The method createInstance() is called to initialize the library as soon as the component initializes.
• To release resources timely, the BarcodeScanner instance is destroyed with the component in the callback ngOnDestroy.
• The method setUIElement() specifies the UI for the library with the native element in barcode-scanner.component.html which we just copied over in the previous step.

Edit the hello-world component

• Add the barcode-scanner component in hello-world.component.html

<div id="UIElement">
    <app-barcode-scanner></app-barcode-scanner>
</div>

• Define the style of the element in hello-world.component.css

#UIElement {
    margin: 2vmin auto;
    text-align: center;
    font-size: medium;
    height: 40vh;
    width: 80vw;
}

Add the hello-world component to app.component.html

Edit the file app.component.html to contain nothing but the following

<app-hello-world></app-hello-world>

• Try running the project.

ng serve -o

If you followed all the steps correctly, you will have a working page that turns one of the cameras hooked to or built in your computer or mobile device into a barcode scanner. However, the found barcodes are not displayed anywhere yet. At the same time, there is a short delay for the initialization of the library during which nothing happens and is not user-friendly. The following takes care of these two issues.

Make it more user friendly

• Change the code in hello-world.component.html like this

<div id="UIElement">
    <span style='font-size:x-large' *ngIf="!libLoaded">Loading Library...</span>
    <app-barcode-scanner *ngIf="bShowScanner" (appendMessage)="appendMessage($event)"></app-barcode-scanner>
</div>
<input id="resultText" type="text" [value]="resultValue" readonly="true">

• Add style for the “input” element in hello-world.component.css

#resultText {
    display: block;
    margin: 0 auto;
    padding: 0.4rem 0.8rem;
    color: inherit;
    width: 80vw;
    border: none;
    font-size: 1rem;
    border-radius: 0.2rem;
    text-align: center;
}

• Also, in hello-world.component.ts, write the following code

import DBR from '../dbr';

export class HelloWorldComponent implements OnInit {
  bShowScanner = false;
  resultValue = "";
  libLoaded = false;
  constructor() { }
  async ngOnInit(): Promise<void> {
    try {
      //Load the library on page load to speed things up.
      await DBR.BarcodeScanner.loadWasm();
      this.libLoaded = true;
      this.showScanner();
    } catch (ex) {
      alert(ex.message);
      throw ex;
    }
  }
  showScanner(): void {
    this.bShowScanner = true;
  }
  hideScanner(): void {
    this.bShowScanner = false;
  }
  appendMessage(message) {
    switch (message.type) {
      case "result":
        this.resultValue = message.format + ": " + message.text;
        break;
      case "error":
        this.resultValue = message.msg;
        break;
      default: break;
    }
  }
}

NOTE :

• The method loadWasm() initializes the library in the background. The scanner UI is only shown when the initialization finishes.
• The method appendMessage() is used to show the result text on the page.

• Add an EventEmitter in barcode-scanner.component.ts and use the event onFrameRead to return the results.

import { Component, OnInit, EventEmitter, Output, ElementRef } from '@angular/core';

export class BarcodeScannerComponent implements OnInit {
  //Omitted code...
  @Output() appendMessage = new EventEmitter();
  async ngOnInit(): Promise<void> {
    try {
      //Omitted code...
      scanner.setUIElement(this.elementRef.nativeElement);
      scanner.onFrameRead = results => {
        for (let result of results) {
          this.appendMessage.emit({ format: result.barcodeFormatString, text: result.barcodeText, type: "result" });
        }
      };
      await scanner.open();
    } catch (ex) {
      this.appendMessage.emit({ msg: ex.message, type: "error" });
      console.error(ex);
    }
  }
  //Omitted code...
}

NOTE :

• The event onFrameRead is triggered upon reading of each frame. If barcodes are found on that frame, the results will be returned and shown on the page.

After the above changes, the application is made more user-friendly and the barcode text is displayed on the page right away. You can start implementing your own business workflow and make the application useful.