In this article you will learn how to create Visual Web Part in SharePoint 2013 with external JS and CSS files.
Introduction In this article I have explained how we can create the Visual Web Part in SharePoint 2013 using Visual Studio 2012. It will be good idea to store our JS and CSS files externally, so that we can avoid most of the deployments as we can directly update our JS and CSS files if we have access to the site. In the following sample I have also explained how we can incorporate our external JS and CSS files in Visual Web Part. Steps to create Visual Web Part
SharePoint Online And Office 365 Administration