Js判断浏览器进度条是否到底部

window.onscroll = function () {
      //变量scrollTop是滚动条滚动时，距离顶部的距离
      var scrollTop =
        document.documentElement.scrollTop || document.body.scrollTop;
      //变量windowHeight是可视区的高度
      var windowHeight =
        document.documentElement.clientHeight || document.body.clientHeight;
      //变量scrollHeight是滚动条的总高度
      var scrollHeight =
        document.documentElement.scrollHeight || document.body.scrollHeight;
      //滚动条到底部的条件
      if (scrollTop + windowHeight == scrollHeight) {
        //写后台加载数据的函数
        console.log(
          "距顶部"  scrollTop +"可视区高度" +windowHeight +"滚动条总高度" +scrollHeight
        );
      }
    };