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class="row"><div class="col docItemCol_3FnS"><div class="docItemContainer_33ec"><article><div class="tocCollapsible_1PrD tocMobile_3Hoh"><button type="button" class="clean-btn tocCollapsibleButton_2O1e">On this page</button></div><div class="markdown"><header><h1>浏览器的重排重绘</h1></header><h2><a aria-hidden="true" tabindex="-1" class="anchor anchor__h2 anchorWithStickyNavbar_31ik" id="相关问题"></a>相关问题<a class="hash-link" href="#相关问题" title="Direct link to heading">#</a></h2><ul><li>如何提升页面渲染性能</li><li>如何减少页面重排重绘</li><li>哪些行为会引起重排/重绘</li></ul><h2><a aria-hidden="true" tabindex="-1" class="anchor anchor__h2 anchorWithStickyNavbar_31ik" id="回答关键点"></a>回答关键点<a class="hash-link" href="#回答关键点" title="Direct link to heading">#</a></h2><p><code>渲染性能</code> <code>Layout</code> <code>Paint</code></p><p>浏览器渲染大致分为四个阶段，其中在解析 HTML 后，会依次进入 Layout 和 Paint 阶段。<strong>样式或节点的更改，以及对布局信息的访问等</strong>，都有可能导致重排和重绘。而重排和重绘的过程在<strong>主线程</strong>中进行，这意味着不合理的重排重绘会导致<strong>渲染卡顿，用户交互滞后</strong>等性能问题。</p><h2><a aria-hidden="true" tabindex="-1" class="anchor anchor__h2 anchorWithStickyNavbar_31ik" id="知识点深入"></a>知识点深入<a class="hash-link" href="#知识点深入" title="Direct link to heading">#</a></h2><h3><a aria-hidden="true" tabindex="-1" class="anchor anchor__h3 anchorWithStickyNavbar_31ik" id="1-什么是重排重绘"></a>1. 什么是重排重绘<a class="hash-link" href="#1-什么是重排重绘" title="Direct link to heading">#</a></h3><p><img src="https://user-images.githubusercontent.com/17002181/126033732-d5002255-1c88-4dee-9371-da166aacdca9.png" alt="image"></p><p><strong>Layout（布局）</strong></p><blockquote><p>指浏览器计算各元素的几何信息，确定元素的大小以及在页面中的位置等信息的过程。</p></blockquote><p><strong>Paint（绘制/栅格化）</strong></p><blockquote><p>指将渲染树中的每个节点转换成屏幕上的实际像素的过程。</p></blockquote><p>浏览器从获取文档、样式、脚本等内容，到最终渲染结果到屏幕上，需要经过如图所示的步骤。而 DOM 或 CSSOM 被修改，会导致浏览器重复执行图中的步骤。重排和重绘，本质上指的就是分别重新触发 Layout 和 Paint 的过程，且重排必定导致重绘。</p><h4><a aria-hidden="true" tabindex="-1" class="anchor anchor__h4 anchorWithStickyNavbar_31ik" id="引起重排重绘的常见操作"></a>引起重排/重绘的常见操作<a class="hash-link" href="#引起重排重绘的常见操作" title="Direct link to heading">#</a></h4><ol><li>外观有变化时，会导致<strong>重绘</strong>。相关的样式属性如 <code>color</code> <code>opacity</code> 等。</li><li>布局结构或节点内容变化时，会导致<strong>重排</strong>。相关的样式属性如 <code>height</code> <code>float</code> <code>position</code> 等。<ul><li>盒子尺寸和类型。</li><li>定位方案（正常流、浮动和绝对定位）。</li><li>文档树中元素之间的关系。</li><li>外部信息（如视口大小等）。</li></ul></li><li>获取布局信息时，会导致<strong>重排</strong>。相关的方法属性如 <code>offsetTop</code> <code>getComputedStyle</code> 等。</li></ol><h3><a aria-hidden="true" tabindex="-1" class="anchor anchor__h3 anchorWithStickyNavbar_31ik" id="2-如何减少重排重绘"></a>2. 如何减少重排重绘<a class="hash-link" href="#2-如何减少重排重绘" title="Direct link to heading">#</a></h3><p><img src="https://user-images.githubusercontent.com/17002181/126033739-3e689aab-fcd8-4928-9e6d-6a047ab2a8c9.png" alt="image"></p><h4><a aria-hidden="true" tabindex="-1" class="anchor anchor__h4 anchorWithStickyNavbar_31ik" id="意义"></a>意义<a class="hash-link" href="#意义" title="Direct link to heading">#</a></h4><p>大多数显示器的刷新率是 60FPS（frames per second）。理想情况下，浏览器需要在 1/60 秒内完成渲染阶段并交付一帧。这样用户就会看到一个交互流畅的页面。</p><p>在交互阶段，页面更新（一般是通过执行 JavaScript 来触发）通常会触发重排和重绘。为了提升浏览器渲染效率，应当尽可能减少重绘重排，降低浏览器渲染耗费的时间，尽快将内容渲染到屏幕上。</p><h4><a aria-hidden="true" tabindex="-1" class="anchor anchor__h4 anchorWithStickyNavbar_31ik" id="解决方案"></a>解决方案<a class="hash-link" href="#解决方案" title="Direct link to heading">#</a></h4><ol><li>对 DOM 进行批量写入和读取（通过虚拟 DOM 或者 DocumentFragment 实现）。</li><li>避免对样式频繁操作，了解常用样式属性触发 Layout / Paint / Composite 的<a href="https://csstriggers.com/" target="_blank" rel="noopener noreferrer">机制</a>，合理使用样式。</li><li>合理利用特殊样式属性（如 transform: translateZ(0) 或者 will-change），将渲染层提升为合成层，开启 GPU 加速，提高页面性能。</li><li>按需缓存布局信息，避免频繁读取。</li></ol><p>另外，可以借助 DevTools Performance 面板来查看产生重排重绘任务占用主线程的情况和调用代码。</p><h2><a aria-hidden="true" tabindex="-1" class="anchor anchor__h2 anchorWithStickyNavbar_31ik" id="参考资料"></a>参考资料<a class="hash-link" href="#参考资料" title="Direct link to heading">#</a></h2><ol><li><a href="https://developers.google.com/web/fundamentals/performance/critical-rendering-path/render-tree-construction?hl=zh-cn" target="_blank" rel="noopener noreferrer">渲染树构建、布局及绘制</a></li><li><a href="https://developers.google.com/web/fundamentals/performance/rendering/avoid-large-complex-layouts-and-layout-thrashing" target="_blank" rel="noopener noreferrer">避免大型、复杂的布局和布局抖动</a></li><li><a href="https://csstriggers.com/" target="_blank" rel="noopener noreferrer">CSS 属性触发布局、绘制及合成的数据</a></li><li><a href="https://gist.github.com/paulirish/5d52fb081b3570c81e3a" target="_blank" rel="noopener noreferrer">What forces layout / reflow</a></li></ol></div></article><nav class="pagination-nav docusaurus-mt-lg" aria-label="Docs pages navigation"><div class="pagination-nav__item"><a class="pagination-nav__link" href="/awesome-interview/book1/browser-cross-origin"><div class="pagination-nav__sublabel">Previous</div><div class="pagination-nav__label">« 浏览器：浏览器跨域</div></a></div><div 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