估计导航用的fixed定位吧,
var windheight =window.innerHeight;
var bottomx = document.getElementById('bottomx'); //底部导航
window.onresize(function(){ var docheight = window.innerHeight;
if(docheight < windheight){
bottomx.style.position = 'static';
}else{
bottomx.style.position = 'fixed';
}
})