他报这个问题
function checkscrollside(){
var oParent=document.getElementById('main');
var aPin=getByClass(oParent,'pin');
var lastPinH=aPin[aPin.length-1].offsetTop+Math.floor(aPin[aPin.length-1].offsetHeight/2);
var scrollTop=document.documentElement.scrollTop||document.body.scrollTop；
var documentH=document.documentElement.clientHeight;//页面高度
return (lastPinH<scrollTop+documentH)?true:false;//到达指定高度后 返回true，触发waterfall()函数
}
function check(){
var oPraent=document.getElementById('main');
var oBox=getByClass(oPraent,'box');
var lastBOxH=oBox[oBoxs.length-1].offsetTop+Math.floor(oBoxs[oBoxs.length-1].offsetHeight/2);
var scrollTop=document.body.scrollTop || document.documentElement.scrollTop;
var height=document.body.clientHeight || document.documentElement.clientHeight;
return (lastBOxH<scrollTop+height)?true:false;
}