A universal definition pattern for JavaScript libraries. Supports require(), AMD, and browser.

universal-definition-pattern.js

;(function() {
  function myModule() {
  }
  
  if (typeof module !== 'undefined' && typeof module.exports !== 'undefined') {
    module.exports = myModule;
  }
  else {
    if (typeof define === 'function' && define.amd) {
      define([], function() {
        return myModule;
      });
    }
    else {
      window.myModule = myModule;
    }
  }
})();

What's the point of declaring the var in the global scope?

So that it won't interfere with module bundlers that do weird things with window.