Javascript module definition with requirejs.

index.html

<script src="require.js"></script>
<script src="main.js"></script>

main.js

requirejs.config({
    baseUrl: './'
});

require(['math'], function(Math) {
  console.log(Math.sum(1, 2));
});

math.js

define([], function() {
    return {
      sum: function() {
          var total = 0;
          for (var idx in arguments) {
              total += arguments[idx];
          }
          return total;
      }
    };
});