title: Can we transpile dart code to multiple JS files?
body: <p>Let's say that a developer has created a general-purpose Dart library, aimed at the client, that contains a large number of class and functionality definitions, of which only a small subset is ever expected to be used in a single web page.</p>
  
  <p>As a Javascript example, Mathjax provides files that contain a large amount of functionality related to displaying mathematical expressions in the browser, though any given web page displaying mathematical expressions is likely to only use a very small amount of the functionality defined by Mathjax. Thus, what page authors tend to do is to link each page they create to a single copy of the large, general-purpose JS file (in the page header, for example) and to then write their own, usually relatively small JS files defining behaviour particular to the page. They can thus potentially have hundreds of pages each linking to a single general-purpose JS file.</p>
  
  <p>When we transpile Dart to JS, however, the output is a single, large JS file that appears to contain the functionality of any dependencies along with the behaviour desired for the particular page. If we had hundreds of pages, each linked to their own dart2js-produced JS file, we appear to have a tremendous amount of redundancy in the code. Further, if we need to make a change to the general-purpose library, it seems that we would have to regenerate the JS for each of the pages. (Or maybe I completely misunderstand things.)</p>
  
  <p>My question is: is it possible to transpile Dart code to multiple JS files? For example, Dart code for a given page might be transpiled into one JS file containing the dependency functionality (that many pages can link to) and one small JS file defining the behaviour particular to the page? </p>