Capitalize First Letter In String

var str = "actionscript";

function upperCase(str:String) : String {
 var firstChar:String = str.substr(0, 1); 
 var restOfString:String = str.substr(1, str.length); 
    
 return firstChar.toUpperCase()+restOfString.toLowerCase(); 
}

trace(upperCase(str)); //Outputs Actionscript