gistfile1.js

function importModule(target, module) {
  for (var method in module) 
    target[method] = module[method]
}

BASE = (function() {
  var exports = {
    getFoo: function() { return 'foo' }
  }
  return exports
})()

FOO = (function() {
  importModule(this, BASE)
  var exports = {
    logFoo: function(x) { console.log(getFoo()) }
  }
  return exports
})()

importModule(window, FOO)
logFoo()