function getsupportedprop(proparray){

    var root=document.documentElement; //reference root element of document

    for (var i=0; i<proparray.length; i++){ //loop through possible properties

        if (proparray[i] in root.style){ //if property exists on element (value will be string, empty string if not set)

            return proparray[i]; //return that string

        }

    }

}

var boxshadowprop=getsupportedprop([ 'OBoxShadow','WebkitTransform','MozTransform']);