Where should an EventListener be added in an Angular Service Worker?

Question

Where should an EventListener be added in an Angular Service Worker?

I am currently in the process of developing an Angular Progressive Web Application (PWA) with offline capabilities. While I have made significant progress, I am facing challenges regarding events for the service worker. Specifically, I am unsure about where to correctly implement the addEventListener(..). Most tutorials suggest using a separate service-worker.js file, but that approach feels awkward to me within a TypeScript environment. Moreover, I would like to leverage my Angular Services to interact with the backend, which seems unattainable from a standalone .js file.

In an attempt to address this issue, I created a Service to register a periodicSync and tried to listen to the event. Although the periodic sync is successfully registered in Chrome, the event is not being captured by the listener.

export class SyncService{

constructor(indexedDbService: IndexedDbService, apiService: ApiService)
{}

   public RegisterSyncStuff(){
    //Works fine
    const registration : any = await navigator.serviceWorker.ready;
    try {
        await registration.periodicSync.register('download-stammdaten',{
           minInterval:  30 * 1000,
         });
     } catch {
        Console.log('no periodicSync possible')
     }
     //Does not work at all. 
     addEventListener('periodicSync', () => {
         let stuffToStore = this.apiService.getStuff();
         indexDbSerivce.StoreStuff(stuffToStore);
     })
  }

}

angular typescript angular-service-worker service-worker-events

Answer 1

Answer №1

In a TypeScript environment, you can develop the worker, but in the browser it runs as a *.js file.

To establish communication between the service-worker.js file and another part of your code, utilize event listeners and posting messages as shown below:

service-worker.js

addEventListener('message', ({data}) => {
  if (data) {
    console.log('Hello from worker!')
    let newDataInArray = [data]
    postMessage(newDataInArray);
  }
});

Consider a DataService module like data-service.ts

import { Injectable } from '@angular/core';

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

  someDataInService: Data = {data};

  constructor() {}

  sendDataToWorker() {
    runWorker(this.someDataInService);
  }

  async runWorker(data: Data) {
    if (typeof Worker !== 'undefined') {

      // Spawn a worker
      const worker = new Worker(new URL('./app.worker', import.meta.url)); 

      // Send data to the worker
      worker.postMessage(data); 

      // On message return from worker
      worker.onmessage = (dataInArray) => { 
        // manipulate dataInArray here
      };
    } else {
      // Handle fallback scenario
    }
  }
}

If a worker is already spawned, there is no need to create a new one unless multiple instances are preferred. Reuse the existing worker by simply posting a message to the instance using worker.postMessage().

Answer 2

In a TypeScript environment, you can develop the worker, but in the browser it runs as a *.js file.

To establish communication between the service-worker.js file and another part of your code, utilize event listeners and posting messages as shown below:

service-worker.js

addEventListener('message', ({data}) => {
  if (data) {
    console.log('Hello from worker!')
    let newDataInArray = [data]
    postMessage(newDataInArray);
  }
});

Consider a DataService module like data-service.ts

import { Injectable } from '@angular/core';

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

  someDataInService: Data = {data};

  constructor() {}

  sendDataToWorker() {
    runWorker(this.someDataInService);
  }

  async runWorker(data: Data) {
    if (typeof Worker !== 'undefined') {

      // Spawn a worker
      const worker = new Worker(new URL('./app.worker', import.meta.url)); 

      // Send data to the worker
      worker.postMessage(data); 

      // On message return from worker
      worker.onmessage = (dataInArray) => { 
        // manipulate dataInArray here
      };
    } else {
      // Handle fallback scenario
    }
  }
}

If a worker is already spawned, there is no need to create a new one unless multiple instances are preferred. Reuse the existing worker by simply posting a message to the instance using worker.postMessage().

Where should an EventListener be added in an Angular Service Worker?

Answer №1

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