1.判断滚动条是否到达底部

1.新建一个lib文件夹

2.建一个base.js的文件(封装)

function onReachBottom(){
     var scrollHeight=$(document).height();
    var scrollTop=$(document).scrollTop();
    var availHeight=$(window).clientHeight;
     return (Math.ceil(scrollTop+availHeight)==scrollHeight)?true:false;
}

3.css样式

<script src="lib/base.js"></script>
    <style>
        *{margin: 0;padding: 0}
        body{
            height: 1500px;
            background: red;
        }
        div{
            height: 1000px;
            background: green;
        }
    </style>

    <div>
    </div>
    <!-- 判断滚动条是否到达底部 -->
    <script>
            /*原生*/
         /*  var scrollHeight=document.documentElement.scrollHeight;
        console.log(scrollHeight)
        window.onscroll=function(){
            var scrollTop=Math.ceil(document.documentElement.scrollTop);//四舍五入
            var availHeight=document.documentElement.clientHeight;  //屏幕的高度
            if(scrollTop+availHeight==scrollHeight){
                console.log("到达底部")
            }
        } */
        window.onscroll=function(){
            console.log(onReachBottom())
        }
    </script>

4.原生

<div>
</div>
<script>
     var scrollHeight=document.documentElement.scrollHeight;
        console.log(scrollHeight)
        window.onscroll=function(){
            var scrollTop=Math.ceil(document.documentElement.scrollTop);//四舍五入
            var availHeight=document.documentElement.clientHeight;  //屏幕的高度
            if(scrollTop+availHeight==scrollHeight){
                console.log("到达底部")
            }
        }
</script>

5.Math

Math.ceil()  上取整
Math.floor()  下取整
Math.round()    四舍五入取整

        var a=12.54;
        console.log(Math.ceil(a))   //13
        console.log(Math.floor(a))  //12
        console.log(Math.round(a))  //13