``` div{ overflow:auto; background:orange; width: 200px; height: 200px; padding:50px; } ``` ``` <div id="div"> hello world </div> <script> console.log(div.scrollHeight) //300 居然要包括padding </script> ``` 视口scrollTop和一屏宽度 兼容 ``` var scrollWidth = Math.max(document.documentElement.scrollWidth, document.body.scrollWidth); var clientWidth = document.documentElement.clientWidth || document.body.clientWidth; ```