feat: Rebase master with beacon transport

Author: HazAT

packages/browser/src/backend.ts

@@ -1,10 +1,10 @@
 import { Backend, logger, Options, SentryError } from '@sentry/core';
 import { SentryEvent, SentryEventHint, SentryResponse, Severity, Status, Transport } from '@sentry/types';
 import { isDOMError, isDOMException, isError, isErrorEvent, isPlainObject } from '@sentry/utils/is';
-import { supportsFetch } from '@sentry/utils/supports';
+import { supportsBeacon, supportsFetch } from '@sentry/utils/supports';
 import { eventFromPlainObject, eventFromStacktrace, prepareFramesForEvent } from './parsers';
 import { computeStackTrace } from './tracekit';
-import { FetchTransport, XHRTransport } from './transports';
+import { BeaconTransport, FetchTransport, XHRTransport } from './transports';
 
 /**
  * Configuration options for the Sentry Browser SDK.
@@ -149,11 +149,16 @@ export class BrowserBackend implements Backend {
       const transportOptions = this.options.transportOptions
         ? this.options.transportOptions
         : { dsn: this.options.dsn };
-      this.transport = this.options.transport
-        ? new this.options.transport({ dsn: this.options.dsn })
-        : supportsFetch()
-          ? new FetchTransport(transportOptions)
-          : new XHRTransport(transportOptions);
+
+      if (this.options.transport) {
+        this.transport = new this.options.transport({ dsn: this.options.dsn });
+      } else if (supportsBeacon()) {
+        this.transport = new BeaconTransport(transportOptions);
+      } else if (supportsFetch()) {
+        this.transport = new FetchTransport(transportOptions);
+      } else {
+        this.transport = new XHRTransport(transportOptions);
+      }
     }
 
     return this.transport.send(event);