Test CSS3 Support with JS

.js

var supports = (function() {
   var div = document.createElement('div'),
      vendors = 'Khtml Ms O Moz Webkit'.split(' '),
      len = vendors.length;
 
   return function(prop) {
      if ( prop in div.style ) return true;
 
      prop = prop.replace(/^[a-z]/, function(val) {
         return val.toUpperCase();
      });
 
      while(len--) {
         if ( vendors[len] + prop in div.style ) {
            // browser supports box-shadow. Do what you need.
            // Or use a bang (!) to test if the browser doesn't.
            return true;
         } 
      }
      return false;
   };
})();
 
if ( supports('textShadow') ) {
   document.documentElement.className += ' textShadow';
}

This function will test whether or not the browser supports a specified CSS3 property, like "border-radius."

Note that, when passing the property, omit the dash. So, instead of "border-radius," pass "borderRadius" (or "BorderRadius").