Please try with a modern version of Firefox. 51 is not supported and hasn't been for sometime. The current version is 63.0.3

It also looks like the current version of Angular is 7, not 6. Please update that as well.

Hi sanjivmt, Angular only claims to support the "latest" release of Firefox ([https://angular.io/guide/browser-support https://angular.io/guide/browser-support]). Since Angular 6 was released in May 2018, presumably they tested in Firefox 59 for that cycle, and possibly in the Extended Support Release of Firefox 52. I don't know how your organization chooses versions to test, but I suggest: (1) Current developer edition and beta releases ([https://www.mozilla.org/firefox/channel/desktop/ https://www.mozilla.org/firefox/channel/desktop/]) (2) Current stable release (63 - [https://www.mozilla.org/firefox/all/]) (3) Current Extended Support Release (ESR) (60 - [https://www.mozilla.org/firefox/organizations/all/ https://www.mozilla.org/firefox/organizations/all/]) (4) If you support customers on Windows XP or Vista, the last Firefox 52 ESR release (Firefox won't update beyond that release on those platforms) If your team has a lot of idle time to test other releases, that's interesting for them, but probably not so much for your customers.