Trying to understand traceur's module transpilation output

README.md

The AMD output of traceur has me a bit confused. The return value looks a lot like an ES6 class - shouldn't this be converting all the way to ES5? FWIW, my options (to traceur) are:

{
  modules: "amd",
	outputLanguage: 'es5'
}

AMDOutput.js

define([], function() {
  "use strict";
  var myVar = {};
  var $__default = myVar;
  return {
    get default() {
      return $__default;
    },
    __esModule: true
  };
});

ES6Example.js

var myVar = {};

export default myVar;

@rauschma, I believe your CommonJS cycle example actually would work properly. It has the potential to cause an infinite loop depending on how you fill in the blanks, but so does the ES6 version. Could you come up with another example that can be run to show the difference?

@eventualbuddha You may be right. I’ll have to give this more thought (which will take a while – busy ATM).

@eventualbuddha: ES6 and (node flavored) CJS both have different cyclic dependency strategies so

ES6 cyclic dependencies that don't work in CJS

//even.js

  import { odd } from './odd'

  export var counter = 0;

  export function even(n) {
    counter++;
    return n == 0 || odd(n - 1);
  }

//odd.js

  import { even } from './even';

  export function odd(n) {
    return n != 0 && even(n - 1);
  }

//app.js
import { even } from './even';
even(); //this works

CJS circular dependencies that don't work in ES6

//a.js
exports.obj = {};
var b = require('./b');
b.something();

//b.js
var a = require('./a');
a.obj.val = 'asdf';
exports.something = function() {};

//app.js
require('./a'); // this doesn't throw

Agreed with @eventualbuddha, that example would work because of partially loaded modules.

Modules are cached after the first time they are loaded. This means (among other things) that every call to require('foo') will get exactly the same object returned, if it would resolve to the same file. Multiple calls to require('foo') may not cause the module code to be executed multiple times. This is an important feature. With it, "partially done" objects can be returned, thus allowing transitive dependencies to be loaded even when they would cause cycles.

edit: This was posted way after composing it, and a few comments were posted before it.