title: Upgrading an ExtJS application from 4.1.2 to 6.x
body: <p>I'm acquiring an existing application written in ExtJS 4.1.2. It's a very large code base. The 4.1.2 application was built without CMD -- the sources are added directly to index.html. </p>
  
  <p>Without having much of an ExtJS background, I have the following two questions:</p>
  
  <p>1) Does it make sense to upgrade to 5.x first and then go from 5.x to 6.x? Or is it safe to go directly from 4.1.2 to 6.x?</p>
  
  <p>2) Should a new project be created and manually copied over, or can I just update the sources, in theory, to point to the new extjs lib, and back peddle fixing all client code that's broken or no longer compatible? </p>
  
  <p>I haven't followed the history of ExtJS much, so I'm not sure if upgrading two major revisions is even feasible with this framework. </p>
  
  <p>What's the best approach if CMD isn't being used in the existing app?</p>