为啥第一种情况打印出来是undefined,xh，第二种情况打印出来是xm，xh

var name='xm';

        var age=18;

        function fn(argument){

            console.log(name);  

            var name='xh';

            var age=10;

            console.log(name);

        }

        fn();   

var name = "xm"

        var age = 18

        function fn() {

            console.log(name);

            name = "xh";

            console.log(name);

        }

        fn();