Javascript - accessing namespace in different files

I can do this in node.js

var module = require('../path/module')
module.functionname()

So I thought I'd like to do that in client side Javascript to organize things slightly. So each of my files now has a namespace. So say login.js has a namespace login.

My question is, what's the best way in ECMAScript 5 to implement something alongs these lines?

What you are trying to achieve can be done with AMDs (asynchronous module definitions). Check out RequireJS for that: http://requirejs.org/

With Require.js you can basically define a set of dependencies, let them get loaded asynchronously and execute code once all stuff was loaded nicely:

require(['dependency1.js', 'dependency2.js'], function(dep1, dep2) {
  console.log(dep1.functionname())
})

The dependency will then declare it's functionalities with require's define method:

define(['a/possible/dependency.js'], function() {
   return {
     functionname: function() { return 1 }
   }
})