poopoo
In my talk, “Scalable >JavaScript Application Architecture” (video, slides), I made the point that your application should never need to know which browser it’s running in. Application logic should be written one way for all browsers in order to keep the code maintainable. If you’re using native APIs in your application logic, you can’t help but know what browser is being used because you need to account for browser differences. That means your application logic will always need to be updated as new browsers and new browser versions are released. That’s a recipe for disaster.
You should absolutely be using a JavaScript library to abstract away browser differences for you. That is the appropriate location in your JavaScript architecture for browser-specific code to exist. Libraries like jQuery, YUI, and Dojo abstract away browser differences behind facades, which allow you to focus on building your application logic in a browser-agnostic way. This gives you a great advantage over using native APIs directly: Browser incompatibilities can be changed within the library and the rest of your application logic doesn’t have to change at all. What’s more, these popular JavaScript libraries are actively maintained and tested against new browsers, so upgrading is all you have to do to get the latest fixes. In a world where JavaScript’s applications are getting more and more complex, using a JavaScript library gives you a big advantage as your application continues to grow and evolve.