title: how can I remove unused code when I build my bundle?
body: <p>I am not sure how to organize my js code.<br>
  Our front end is customized to different customers. Majority of the base code is common across all customers. However there are cases where certain functionality is overridden for each customer.<br>
  For example if we have 2 functions Function1 and Function2.<br>
  Customer1 uses Function1 while Customer2 uses Function2. How can I make sure that when I build the code for Customer, Function2 will not be included in the bundle? And when I build the code for Customer2, then Function1 will not be included int he bundle?</p>
  
  <p>The other option I have, and that I am trying to avoid, is to have a separate code repo for each customer.</p>