Preserving methods during dart2js minification and tree-shaking

Question

I have a few files that I have written in dart that I want to compile to javascript and include in a few html files that are running in my Android application.

The files consist of a main method, then there is an api layer with 3 functions that other javascript code will call at run-time. It's very important that I include as little of dart's libraries as possible (so tree-shaking is a must), and when the tree-shaking / minification process happens, I need to ensure that the 3 api layer functions don't get renamed / optimized out because it thinks they aren't being called?

How do I tell dart2js to leave the signature of certain functions alone, and not to prune them out because it thinks they aren't being used?

Answer 1

You can use the dart:js library's context property, a JsObject which allows you to expose variables and methods from dart to JavaScript, and will be preserved by dart2js. In your main method, simply include context['jsMethodName'] = dartMethodName, and then call it in your JavaScript. Here's an example:

library.dart

import 'dart:js';

void main(){
  print("main called!");
  context['myMethod'] = myMethod;
}

void myMethod(){
  print("My Method Called!");
}

index.html

<script src="library.dart.js"></script>
<script>
  console.log(myMethod());
</script>