title: JavaScript compatibility libraries
body: <p>Are there javascript libraries that provide forward compatibility with particular implementations?  For example, such a library could provide features present in JavaScript 1.6 in a way that's portable across various browsers.  It should take advantage of native support for that functionality when available.</p>
  
  <p>Some of the frameworks like JQuery or Prototype provide features that are identical to features in newer versions of JS, but I'd like to both cut down on the size of the library I'm using and ensure full compliance with a standard or published version.</p>
  
  <p>Do libraries such as this exist?  Google and wikipedia don't have much to say on this topic.</p>