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: Element.shadowRoot
+slug: Web/API/Element/shadowRoot
+tags:
+  - プロパティ
+  - リファレンス
+  - 要素
+  - 試験的
+translation_of: Web/API/Element/shadowRoot
+---
+<p>{{APIRef('Shadow DOM')}} {{SeeCompatTable}}{{draft}}</p>
+
+<p>読み取り専用のプロパティである<code>Element.shadowRoot</code>は、そのエレメントによってホストされたshadow rootへの読み取りアクセスを提供します。既に存在している要素にshadow rootを追加する場合は {{domxref('Element.attachShadow')}} を使用してください。</p>
+
+<h2 id="Syntax" name="Syntax">文法</h2>
+
+<pre class="syntaxbox">var <em>shadowroot =</em><em> element</em>.shadowRoot;
+</pre>
+
+<h3 id="値">値</h3>
+
+<p>{{domxref('ShadowRoot')}} オブジェクトです。 アタッチされた時の{{DOMxRef("ShadowRoot.mode", "mode")}} に <code>closed</code> が指定された場合には  <code>null</code> となります。</p>
+
+<h2 id="Examples">Examples</h2>
+
+<p>The following snippets are taken from our <a href="https://github.com/mdn/web-components-examples/tree/master/life-cycle-callbacks">life-cycle-callbacks</a> example (<a href="https://mdn.github.io/web-components-examples/life-cycle-callbacks">see it live also</a>), which creates an element that displays a square of a size and color specified in the element's attributes.</p>
+
+<p>Inside the <code>&lt;custom-square&gt;</code> element's class definition we include some life cycle callbacks that make a call to an external function, <code>updateStyle()</code>, which actually applies the size and color to the element. You'll see that we are passing it <code>this</code> (the custom element itself) as a parameter.</p>
+
+<pre class="brush: js">connectedCallback() {
+  console.log('Custom square element added to page.');
+  updateStyle(this);
+}
+
+attributeChangedCallback(name, oldValue, newValue) {
+  console.log('Custom square element attributes changed.');
+  updateStyle(this);
+}</pre>
+
+<p>In the <code>updateStyle()</code> function itself, we get a reference to the shadow DOM using {{domxref("Element.shadowRoot")}}. From here we use standard DOM traversal techniques to find the {{htmlelement("style")}} element inside the shadow DOM and then update the CSS found inside it:</p>
+
+<pre class="brush: js">function updateStyle(elem) {
+  const shadow = elem.shadowRoot;
+  const childNodes = Array.from(shadow.childNodes);
+
+  childNodes.forEach(childNode =&gt; {
+    if (childNode.nodeName === 'STYLE') {
+      childNode.textContent = `
+        div {
+          width: ${elem.getAttribute('l')}px;
+          height: ${elem.getAttribute('l')}px;
+          background-color: ${elem.getAttribute('c')};
+        }
+      `;
+    }
+  });
+}</pre>
+
+<h2 id="仕様">仕様</h2>
+
+<table class="standard-table">
+ <tbody>
+  <tr>
+   <th scope="col">仕様</th>
+   <th scope="col">状態</th>
+   <th scope="col">注脚</th>
+  </tr>
+  <tr>
+   <td>{{SpecName('DOM WHATWG', '#dom-element-shadowroot', 'shadowRoot')}}</td>
+   <td>{{Spec2('DOM WHATWG')}}</td>
+   <td></td>
+  </tr>
+ </tbody>
+</table>
+
+<h2 id="ブラウザ互換性">ブラウザ互換性</h2>
+
+
+
+<p>{{Compat("api.Element.shadowRoot")}}</p>
+
+<h2 id="関連情報">関連情報</h2>
+
+<ul>
+ <li>{{DOMxRef("Element.openOrClosedShadowRoot")}} {{non-standard_inline}}</li>
+</ul>
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