Conditionizr – Intelligent Script, Style And Retina Loader
It has conditional <html> class additions for the browser and its version in use (like
<html class="ie ie8">
Any script and style can be loaded for the defined browsers. Also, similar to
class additions feature, it can add specific classes for retina and non-retina devices.
And, another nice feature is the ability to return the OS of the visitor which is again useful for loading any custom scripts and styles.