1. scroll 事件
    2. resize 事件

    scroll事件在文档或文档元素滚动时触发，主要出现在用户拖动滚动条

    1. window.onscroll = function(e){
    2.     var srcrollHeight = document.documentElement.scrollTop;
    3.     console.log(srcrollHeight);
    4. }
    5. //or
    6. window.addEventListener("scroll",function(){
    7.     var srcrollHeight = document.documentElement.scrollTop;
    8.     console.log(srcrollHeight);
    9. })

    resize事件在改变浏览器窗口大小时触发

    1. window.onresize = function(){
    2.     console.log("窗口发生变化");
    3. }