In this appendix, we looked at the rationale behind version 4 of the ArcGIS API for JavaScript and allayed some concerns about our existing 3.x skills becoming obsolete in the short term. We also considered some of the amazing new features that the API supports, including 3D mapping, vector tile layers, and more. There are plenty more we didn't cover, such as better, easier-to-style widgets, integration with other frameworks like JQuery, and better support for ArcGIS Online and Portal installations, but we would urge you to consult the documentation for further information.
That brings us to the end of the book. We hope we have given you a good enough basis for using the ArcGIS API for JavaScript to encourage you to create some truly outstanding web mapping applications!
