electron/docs/api/service-workers.md

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## Class: ServiceWorkers
> Query and receive events from a sessions active service workers.
Process: [Main](../glossary.md#main-process)<br />
_This class is not exported from the `'electron'` module. It is only available as a return value of other methods in the Electron API._
Instances of the `ServiceWorkers` class are accessed by using `serviceWorkers` property of
a `Session`.
For example:
```js
const { session } = require('electron')
// Get all service workers.
console.log(session.defaultSession.serviceWorkers.getAllRunning())
// Handle logs and get service worker info
session.defaultSession.serviceWorkers.on('console-message', (event, messageDetails) => {
console.log(
'Got service worker message',
messageDetails,
'from',
session.defaultSession.serviceWorkers.getFromVersionID(messageDetails.versionId)
)
})
```
### Instance Events
The following events are available on instances of `ServiceWorkers`:
#### Event: 'console-message'
Returns:
* `event` Event
* `messageDetails` Object - Information about the console message
* `message` string - The actual console message
* `versionId` number - The version ID of the service worker that sent the log message
* `source` string - The type of source for this message. Can be `javascript`, `xml`, `network`, `console-api`, `storage`, `rendering`, `security`, `deprecation`, `worker`, `violation`, `intervention`, `recommendation` or `other`.
* `level` number - The log level, from 0 to 3. In order it matches `verbose`, `info`, `warning` and `error`.
* `sourceUrl` string - The URL the message came from
* `lineNumber` number - The line number of the source that triggered this console message
Emitted when a service worker logs something to the console.
#### Event: 'registration-completed'
Returns:
* `event` Event
* `details` Object - Information about the registered service worker
* `scope` string - The base URL that a service worker is registered for
Emitted when a service worker has been registered. Can occur after a call to [`navigator.serviceWorker.register('/sw.js')`](https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorkerContainer/register) successfully resolves or when a Chrome extension is loaded.
#### Event: 'running-status-changed' _Experimental_
Returns:
* `details` Event\<\>
* `versionId` number - ID of the updated service worker version
* `runningStatus` string - Running status.
Possible values include `starting`, `running`, `stopping`, or `stopped`.
Emitted when a service worker's running status has changed.
### Instance Methods
The following methods are available on instances of `ServiceWorkers`:
#### `serviceWorkers.getAllRunning()`
Returns `Record<number, ServiceWorkerInfo>` - A [ServiceWorkerInfo](structures/service-worker-info.md) object where the keys are the service worker version ID and the values are the information about that service worker.
#### `serviceWorkers.getInfoFromVersionID(versionId)`
* `versionId` number - ID of the service worker version
Returns [`ServiceWorkerInfo`](structures/service-worker-info.md) - Information about this service worker
If the service worker does not exist or is not running this method will throw an exception.
#### `serviceWorkers.getFromVersionID(versionId)` _Deprecated_
* `versionId` number - ID of the service worker version
Returns [`ServiceWorkerInfo`](structures/service-worker-info.md) - Information about this service worker
If the service worker does not exist or is not running this method will throw an exception.
**Deprecated:** Use the new `serviceWorkers.getInfoFromVersionID` API.
#### `serviceWorkers.getWorkerFromVersionID(versionId)` _Experimental_
* `versionId` number - ID of the service worker version
Returns [`ServiceWorkerMain | undefined`](service-worker-main.md) - Instance of the service worker associated with the given version ID. If there's no associated version, or its running status has changed to 'stopped', this will return `undefined`.
#### `serviceWorkers.startWorkerForScope(scope)` _Experimental_
* `scope` string - The scope of the service worker to start.
Returns `Promise<ServiceWorkerMain>` - Resolves with the service worker when it's started.
Starts the service worker or does nothing if already running.
```js
const { app, session } = require('electron')
const { serviceWorkers } = session.defaultSession
// Collect service workers scopes
const workerScopes = Object.values(serviceWorkers.getAllRunning()).map((info) => info.scope)
app.on('browser-window-created', async (event, window) => {
for (const scope of workerScopes) {
try {
// Ensure worker is started
const serviceWorker = await serviceWorkers.startWorkerForScope(scope)
serviceWorker.send('window-created', { windowId: window.id })
} catch (error) {
console.error(`Failed to start service worker for ${scope}`)
console.error(error)
}
}
})
```