navigator.mediaDevices.enumerateDevices().then((devices) => {
    for (var i = 0; i < devices.length; i++) {
      var device = devices[i];
      if (device.kind === 'videoinput') {
        console.log(device);
        this.myDevice = devices[1];          
      }
    }
    console.log(this.myDevice);
  });
  

  <zxing-scanner
    [enable]="scannerEnabled"
    [(device)]="desiredDevice"
    [torch]="torch"
    (torchCompatible)="onTorchCompatible($event)"
    (camerasFound)="camerasFoundHandler($event)"
    (camerasNotFound)="camerasNotFoundHandler($event)"
    (scanSuccess)="scanSuccessHandler($event)"
    (scanError)="scanErrorHandler($event)"
    (scanFailure)="scanFailureHandler($event)"
    (scanComplete)="scanCompleteHandler($event)"
></zxing-scanner>
  

            
<select #selectList (change)="selectCamera(selectList.value)">
  <option *ngFor="let camera of cameras" value={{camera.label}}>
    {{ camera.label }}
  </option>
</select>

<zxing-scanner style="width: 500px;"
  [enable]="scannerEnabled"
  [device]="myDevice"
  (camerasFound)="camerasFoundHandler($event)"
  (scanSuccess)="scanSuccessHandler($event)"
></zxing-scanner>
<p *ngFor="let result of results">{{result}}</p>
  
        

            
  import { Component, inject } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css'],
})
export class AppComponent {
  title = 'qr-reader';
  public cameras:MediaDeviceInfo[]=[];
  public myDevice!: MediaDeviceInfo;
  public scannerEnabled=false;
  public results:string[]=[];

  constructor() {
  }

  camerasFoundHandler(cameras: MediaDeviceInfo[]){
    this.cameras=cameras;
    this.selectCamera(this.cameras[0].label);
  }

  scanSuccessHandler(event:string){
    console.log(event);
    this.results.unshift(event);
  }

  selectCamera(cameraLabel: string){    
    this.cameras.forEach(camera=>{
      if(camera.label.includes(cameraLabel)){
        this.myDevice=camera;
        console.log(camera.label);
        this.scannerEnabled=true;
      }
    })    
  }
}
  
        

            
import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { ZXingScannerModule } from '@zxing/ngx-scanner';

import { AppComponent } from './app.component';

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