<script>

        // // 页面加载的时候触发

        // window.addEventListener("load", function () {

        // })

        //   页面滚动条

        x.style.display = "none";

        window.addEventListener("scroll", function () {

            if (window.pageYOffset > 70) {

                x.style.display = "block";

            } else {

                x.style.display = "none";

            };

        })

        // 页面尺寸发生变化触发事件

        window.addEventListener("resize", function () {

            console.log(window.innerHeight, window.innerWidth);

        });

    </script>