mui方法返回顶部兼容性问题？

在mui上看到另一位大神的返回顶部方法的代码，我就用了，但是发现，在安卓上无法显示，不知道什么问题，特此贴出来，想问下大神们，怎么解决呀？
var scrollToTopBox = document.getElementById('scrollToTop');
//返回按钮tap
scrollToTopBox.addEventListener('tap', function(e) {
e.stopPropagation();
mui('#pullrefresh').pullRefresh().scrollTo(0, 0, 100);//滚动到顶部
});
//Android上监听原生滚动，iOS上监听div滚动，上拉超过一屏后显示按钮，否则隐藏，可自行在条件判断中修改
if (mui.os.android) {
window.addEventListener('scroll', function(e) {
if (window.pageYOffset >= window.innerHeight && scrollToTopBox.classList.contains('hide'))
scrollToTopBox.classList.remove('hide');
else if (window.pageYOffset < window.innerHeight && !scrollToTopBox.classList.contains('hide'))
scrollToTopBox.classList.add('hide');
});
} else {
document.getElementById('pullrefresh').addEventListener('scrollend', function() {
if (mui('#pullrefresh').pullRefresh().y <= window.innerHeight (-1) && scrollToTopBox.classList.contains('hide'))
scrollToTopBox.classList.remove('hide');
else if (mui('#pullrefresh').pullRefresh().y > window.innerHeight (-1) && !scrollToTopBox.classList.contains('hide'))
scrollToTopBox.classList.add('hide');
});
}