//頁面加載完畢觸發(fā)

window.onload = function(){

var time = null;

var obtn = document.getElementById('btn');

obtn.onclick = function(){

//設(shè)置定時器

time = setInterval(function(){

//獲取滾動條與頂部的距離

var osTop = document.documentElement.scrollTop || document.body.scrollTop;

document.documentElement.scrollTop = document.body.scrollTop -=200;

},30);

}

}