代码效果：
窗口扩大、缩小，滚动条上下、左右移动，盒子都居中显示
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>Document</title> <style> * { margin: 0; padding: 0; } body { width: 3000px; height: 3000px; } #box { width: 200px; height: 200px; background: forestgreen; position: absolute; } </style> </head> <body> <div id="box"></div> <script> var box = document.getElementById(‘box‘); function center() { var pageWidth = document.documentElement.clientWidth; // 浏览器可视宽 var pageHeight = document.documentElement.clientHeight; // 浏览器可视高 // 水平居中 box.style.left = document.documentElement.scrollLeft + (pageWidth - box.offsetWidth) / 2 + ‘px‘; // 垂直居中 box.style.top = document.documentElement.scrollTop + (pageHeight - box.offsetHeight) / 2 + ‘px‘; } center(); // 窗口改变事件 window.onresize = center; // 滚动事件 window.onscroll = center; </script> </body> </html>
效果图
原文：https://www.cnblogs.com/shihaiying/p/13275991.html