一组JS返回值为什么不是布尔类型

        function test() {

            var b;

                $.get('Ajax.aspx', function (data) {



                    if ($.trim(data) != "") {

                        alert(data + "z");

                        b= true;

                    }

                    else {

                        alert(data + "j");

                        b= false;

                    }

                    alert(b);//此处结果是 true;

                });

                alert(b);//此处结果是 unfinished

                return b;

        }

为什么返回的是unfinished的？哪里错了？
------解决方案--------------------
首先要理解ajax是个异步的东西
function test() {
            var b;
                $.get('Ajax.aspx', function (data) {
 
                    if ($.trim(data) != "") {
                        alert(data + "z");
                        b= true;
                    }
                    else {
                        alert(data + "j");
                        b= false;
                    }