A few weeks ago, I’ve submitted my first contribution to the community repository of SharePoint Framework solutions, in this case for the extension. This was built with the purpose to send a message to your external users that access your SharePoint site. You can present this message to all your SharePoint sites using the Tenant wide extension list on your Tenant App Catalog.
In some of the SharePoint Framework solutions, it’s important to understand if the user is either or not an external user from your Office 365. With a few lines of code using the PnP.js, we can verify this.