This is a long shot, but is it possible to have a default method or property on a Javascript object, one that gets invoked when you reference a property that doesn't exist?
For example,
foo.js:
export default {
  hello: 'hello',
  world() {
    return 'world';
  },
  defaultProperty() {
    return 'defaultValue';
  }
}
bar.js:
import foo from 'foo.js';
console.log(foo.hello); // 'hello'
console.log(foo.unknownFunction()); // 'defaultValue'
console.log(foo.unknownProperty); // 'defaultValue'