这段代码的执行结果很诡异，还望高手不吝赐教！该怎么处理

这段代码的执行结果很诡异，还望高手不吝赐教！

JScript code

function base() {    this.member = "global";    this.method = function() {        console.log("global method");        return "global method return";    };}(function extend() {    base.call(this);    console.log(this.member);    console.log(this.method());})();

JScript code

globalglobal methodglobal method return

JScript code

global methodglobalglobal method return

HTML code

<script type="text/javascript">              function base() {                this.member = "global";                this.method = function() {                    console.log("global method");                    return "global method return";                };            }            (function extend() {                base.call(this);                console.log(this.member);   //这句输出global ,因为base函数的this.member 就是 "global";                console.log(this.method());  //这句输出 global method  global method return   //lz你可以把这句注释掉就清楚了，            })();        </script>