global.js

/**
 * An export pattern for global objects
 * (to avoid pollution)
 */
// File A
var foo = (function (that) {
  that.bar = 1;

  return that;
}(foo || {}));

// File B
var foo = (function (that) {
  that.baz = 2;

  return that;
}(foo || {}));

// Result is a single object
foo = {
    bar: 1,
    baz: 2
};