If you do much development in CRM and use visual studio for your JS development and deployments you will find yourself missing the native intellisense feature that is so handy to have when using the IDE. However there is a useful solution for those that have also had this issue.
It is an additional .js file that can be added at the beginning of your code that can help with this in Visual Studio. The js library itself is created from the team that created the MSXRMToolkit and can be downloaded at the following location here. http://msxrmtools.com/Xrm.Page/MSXRMTOOLS.Xrm.Page.2016.js
All you need to do is add the file in your visual studio JS file deploy it as a resource and then you can reference it in your other .js files to activate intellisense in your code by dragging it in VS to your js file.
Optionally you can just add the following reference on each of your JS files that you would like to see intellisense in.
/// <reference path=”MSXRMTOOLS.Xrm.Page.2016.js” />
Now you should be able to activate the intellisense options in VS by simply typing in XRM. as shown in the image below.