1. Download The Required JS Files from here .
  2. Paste "XrmPage-vsdoc.js" file to your C Drive.
  3. Open Visual Studio and press Ctrl + N and select Script tab and then open javascript file.

  4. Paste this part of code on the top of your file without quotes "///<reference path="c:/XrmPage-vsdoc.js" />".

  5. Now start writing your JScript code.

  6. Now you have Intellisense Enabled JScript Visual Studio for MS CRM 2011 & 2013.