console 命令行工具 X clear
console
<!DOCTYPE html>
<html>
<head>

</head>
<body>
    <script>
        var o = 2;
        function aa(){
            var a = 5;
            // function bb(){
            //     console.log(o += a);
            // }
            // return bb();
            return function() {
                return console.log(o += a);
            };
        }
        var result=aa();
        result();
        console.log(o);
    </script>
</body>
</html>