延迟是等键盘弹出后再去执行
setTimeout(function () {
(function smoothscroll(){
var currentScroll = document.documentElement.scrollTop || document.body.scrollTop;
if (currentScroll > 0) {
window.requestAnimationFrame(smoothscroll);
window.scrollTo (0,currentScroll - (currentScroll/5));
}
})();
},100)
