THE OLD, OLD WAY
A couple years ago I moved to a large company with an extremely large codebase and eventually needed to work on some big enhancements to one of their web based subsystems. I dug into the code to attempt to figure out what I needed to do to get the job done. I found a huge, un-maintainable mess which was the result of people coming and going and just tacking on bits here and there, then forgetting about it. There was no way I was about to get in there and do the same thing. At this point, I had never used an MV* framework in the browser but I knew that they were probably the answer I was looking for. I started researching and eventually decided on Angular.