From 33058f2b292b3a581333bdfb21b8f671898c5060 Mon Sep 17 00:00:00 2001
From: Peter Bengtsson <mail@peterbe.com>
Date: Tue, 8 Dec 2020 14:40:17 -0500
Subject: initial commit

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+---
+title: DOM allocation example
+slug: Tools/Memory/DOM_allocation_example
+tags:
+  - 内存
+  - 开发者工具
+translation_of: Tools/Memory/DOM_allocation_example
+---
+<div>{{ToolsSidebar}}</div>
+
+<p>这篇文章描述了一个简单的 Web 页面，它被用于阐述内存工具的一些特性。</p>
+
+<p>你可以在这个网页中试试：<a href="https://mdn.github.io/performance-scenarios/dom-allocs/alloc.html">https://mdn.github.io/performance-scenarios/dom-allocs/alloc.html</a>。</p>
+
+<p>它仅仅包含了一个创建大量 DOM 节点的脚本：</p>
+
+<pre class="brush: js">var toolbarButtonCount = 20;
+var toolbarCount = 200;
+
+function getRandomInt(min, max) {
+    return Math.floor(Math.random() * (max - min + 1)) + min;
+}
+
+function createToolbarButton() {
+  var toolbarButton = document.createElement("span");
+  toolbarButton.classList.add("toolbarbutton");
+  // stop Spidermonkey from sharing instances
+  toolbarButton[getRandomInt(0,5000)] = "foo";
+  return toolbarButton;
+}
+
+function createToolbar() {
+  var toolbar = document.createElement("div");
+  // stop Spidermonkey from sharing instances
+  toolbar[getRandomInt(0,5000)] = "foo";
+  for (var i = 0; i &lt; toolbarButtonCount; i++) {
+    var toolbarButton = createToolbarButton();
+    toolbar.appendChild(toolbarButton);
+  }
+  return toolbar;
+}
+
+function createToolbars() {
+  var container = document.getElementById("container");
+  for (var i = 0; i &lt; toolbarCount; i++) {
+    var toolbar = createToolbar();
+    container.appendChild(toolbar);
+  }
+}
+
+createToolbars();
+</pre>
+
+<p>一段表示代码工作流程的伪代码：</p>
+
+<pre>createToolbars()
+    -&gt; createToolbar() // 调用 200 次, 每次创建一个 DIV 元素
+       -&gt; createToolbarButton() // 每次调用 createToolbar() 时，调用 20 次，每次创建一个 SPAN 元素</pre>
+
+<p>它总共创建了 200 个 <code><a href="/en-US/docs/Web/API/HTMLDivElement">HTMLDivElement</a></code> 对象和 4000 个 <code><a href="/en-US/docs/Web/API/HTMLSpanElement">HTMLSpanElement</a></code> 对象。</p>
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