使用闭包保存变量，下次调用不会被销毁（垃圾回收）

<!DOCTYPE html>
<html>
    <head>
        <meta charset=utf-8>
    </head>
    <body>
        <script type="text/javascript">
            const closure = () => {
                // 补全代码
                let conut = 1
                return function() {return conut++}
            }
        </script>
    </body>
</html>