Fix undefined is not a function for String.prototype.startsWith (#2568)

* Fix `undefined is not a function` for `String.prototype.startsWith`

* Changelog entry added

---------

Co-authored-by: Romain Menke <11521496+romainmenke@users.noreply.github.com>

Author: mclack

CHANGELOG.md

@@ -18,6 +18,7 @@
 
 - Update bugsnag-cocoa to [v6.33.1](https//github.com/bugsnag/bugsnag-cocoa/releases/tag/v6.33.1) [#2552](https://github.com/bugsnag/bugsnag-js/pull/2552)
 - Update bugsnag-android to [v6.18.0](https//github.com/bugsnag/bugsnag-android/releases/tag/v6.18.0) [#2556](https://github.com/bugsnag/bugsnag-js/pull/2556)
+- (core): Change `startsWith()` to `indexOf() === 0` to support older browsers [#2568](https://github.com/bugsnag/bugsnag-js/pull/2568)
 
 ### Fixed
 

packages/core/client.js

@@ -169,7 +169,7 @@ class Client {
       // warn about an apikey that is not of the expected format
       if (!/^[0-9a-f]{32}$/i.test(config.apiKey)) errors.apiKey = 'should be a string of 32 hexadecimal characters'
 
-      if (opts.endpoints === undefined && config.apiKey.startsWith(HUB_PREFIX)) {
+      if (opts.endpoints === undefined && config.apiKey.indexOf(HUB_PREFIX) === 0) {
         config.endpoints = {
           notify: HUB_NOTIFY,
           sessions: HUB_SESSION