<aside class="msg message"><span class="msg-symbol">!</span><div class="msg-content">
<p data-line="1" class="code-line">この記事は <a href="https://adventar.org/calendars/10903" target="_blank" rel="nofollow noopener noreferrer">1人 ECMAScript Normative Changes Advent Calendar 2024</a> の 15 日目です。</p>
</div></aside>
<h1 id="typeof-%E3%81%AE-implementation-defined-%E3%82%92%E5%89%8A%E9%99%A4" data-line="4" class="code-line">
<a class="header-anchor-link" href="#typeof-%E3%81%AE-implementation-defined-%E3%82%92%E5%89%8A%E9%99%A4" aria-hidden="true"></a> <code>typeof</code> の implementation-defined を削除</h1>
<p data-line="6" class="code-line">歴史的経緯から <code>typeof</code> の結果に implementation-defined が含まれていました。</p>
<table data-line="8" class="code-line">
<thead data-line="8" class="code-line">
<tr data-line="8" class="code-line">
<th>Type of <em>val</em>
</th>
<th>Result</th>
</tr>
</thead>
<tbody data-line="10" class="code-line">
<tr data-line="10" class="code-line">
<td>Undefined</td>
<td><code>"undefined"</code></td>
</tr>
<tr data-line="11" class="code-line">
<td>Null</td>
<td><code>"object"</code></td>
</tr>
<tr data-line="12" class="code-line">
<td>Boolean</td>
<td><code>"boolean"</code></td>
</tr>
<tr data-line="13" class="code-line">
<td>Number</td>
<td><code>"number"</code></td>
</tr>
<tr data-line="14" class="code-line">
<td>String</td>
<td><code>"string"</code></td>
</tr>
<tr data-line="15" class="code-line">
<td>Symbol</td>
<td><code>"symbol"</code></td>
</tr>
<tr data-line="16" class="code-line">
<td>Object (ordinary and does not implement <code>[[Call]]</code>)</td>
<td><code>"object"</code></td>
</tr>
<tr data-line="17" class="code-line">
<td>Object (standard exotic and does not implement <code>[[Call]]</code>)</td>
<td><code>"object"</code></td>
</tr>
<tr data-line="18" class="code-line">
<td>Object (implements <code>[[Call]]</code>)</td>
<td><code>"function"</code></td>
</tr>
<tr data-line="19" class="code-line">
<td>Object (non-standard exotic and does not implement <code>[[Call]]</code>)</td>
<td>
<strong>Implementation-defined</strong>. Must not be <code>"undefined"</code>, <code>"boolean"</code>, <code>"function"</code>, <code>"number"</code>, <code>"symbol"</code>, or <code>"string"</code>.</td>
</tr>
</tbody>
</table>
<p data-line="21" class="code-line">そして実際に Internet Explorer 10 で <code>"unknown"</code> を返すオブジェクトが存在しました。</p>
<p data-line="23" class="code-line"><span class="embed-block zenn-embedded zenn-embedded-card"><iframe id="zenn-embedded__7b44fda1c32c" src="https://embed.zenn.studio/card#zenn-embedded__7b44fda1c32c" data-content="https%3A%2F%2Fgithub.com%2Ftc39%2Fecma262%2Fissues%2F1440" frameborder="0" scrolling="no" loading="lazy"></iframe></span><a href="https://github.com/tc39/ecma262/issues/1440" style="display:none" target="_blank" rel="nofollow noopener noreferrer">https://github.com/tc39/ecma262/issues/1440</a></p>
<p data-line="25" class="code-line">今となってはこの仕様は不要であるということで、2019年3月にこの implementation-defined を取り除く変更が承認されました。</p>
<p data-line="27" class="code-line"><span class="embed-block zenn-embedded zenn-embedded-card"><iframe id="zenn-embedded__92386364a19b1" src="https://embed.zenn.studio/card#zenn-embedded__92386364a19b1" data-content="https%3A%2F%2Fgithub.com%2Ftc39%2Fecma262%2Fpull%2F1441" frameborder="0" scrolling="no" loading="lazy"></iframe></span><a href="https://github.com/tc39/ecma262/pull/1441" style="display:none" target="_blank" rel="nofollow noopener noreferrer">https://github.com/tc39/ecma262/pull/1441</a></p>


ENCA 15日目: typeof の implementation-defined を削除

typeof の implementation-defined を削除

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