Using this and exports in Underscore

How underscore.js does it

var root = this;

// Export the Underscore object for **CommonJS**, with backwards-compatibility
// for the old `require()` API. If we're not in CommonJS, add `_` to the
// global object.
if (typeof module !== 'undefined' && module.exports) {
  module.exports = _;
  _._ = _;
} else {
  root._ = _;
}