Javascript中arguments和arguments.callee的区别浅析

<script type="text/javascript">        
        function check(args){            
            var ac = args.length; 
            var ex = args.callee.length; 
            document.write("ac:" + ac + '<br>'); 
            document.write("ex:" + ex + '<br>'); 
            if (ac != ex) { 
                document.write("wrong number of arguments: expected: " + ex + "; actually passed" + ac + '<br>'); 
            } 
        } 
        function f(x, y, z) { 
            check(arguments); 
            document.write(x + y + z); 
        }             
    </script> 

<input name="wr" type="button" value="调用" onclick="f(1,2)" /> 

ac:2
ex:3
wrong number of arguments: expected: 3; actually passed2
NaN