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href="/js-misc"><span>その他</span></a></li><script type="application/ld+json">{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"チュートリアル","item":"https://ja.javascript.info/"},{"@type":"ListItem","position":2,"name":"JavaScript 言語","item":"https://ja.javascript.info/js"},{"@type":"ListItem","position":3,"name":"その他","item":"https://ja.javascript.info/js-misc"}]}</script></ol><div class="updated-at" data-tooltip="最終更新日2020年7月12日"><div class="updated-at__content">2020年7月12日</div></div></div><h1 class="main__header-title">BigInt</h1></div></header><div class="content"><article class="formatted" itemscope itemtype="http://schema.org/TechArticle"><meta itemprop="name" content="BigInt"><div itemprop="author" itemscope itemtype="http://schema.org/Person"><meta itemprop="email" content="iliakan@gmail.com"><meta itemprop="name" content="Ilya Kantor"></div><div itemprop="articleBody"><div class="important important_warn"> <div class="important__header"><span class="important__type">A recent addition</span></div> <div class="important__content"> This is a recent addition to the language. You can find the current state of support at <a href="https://caniuse.com/#feat=bigint">https://caniuse.com/#feat=bigint</a>. </div></div> <p><code>BigInt</code> は任意の長さの整数をサポートする特別な数値型です。</p> <p>bigint は <code>n</code> を整数リテラルの末尾に追加するか、文字列や数字などから bigint を作成する関数 <code>BigInt</code> を呼び出すことによって生成されます。</p> <div id="to7jm2rcix" data-trusted="1" class="code-example"> <div class="codebox code-example__codebox"> <div class="codebox__code" data-code="1"> <pre class="line-numbers language-javascript"><code>const bigint = 1234567890123456789012345678901234567890n; const sameBigint = BigInt("1234567890123456789012345678901234567890"); const bigintFromNumber = BigInt(10); // 10n と同じ</code></pre> </div> </div> </div><h2><a class="main__anchor" name="ref-703" href="#ref-703">算術演算子</a></h2><p><code>BigInt</code> はほぼ通常の数値のように扱うことができます。例えば:</p> <div id="dff6myx7vo" data-trusted="1" class="code-example"> <div class="codebox code-example__codebox"> <div class="toolbar codebox__toolbar"> <div class="toolbar__tool"> <a href="#" title="実行" data-action="run" class="toolbar__button toolbar__button_run"></a> </div> <div class="toolbar__tool"> <a href="#" title="サンドボックで開く" target="_blank" data-action="edit" class="toolbar__button toolbar__button_edit"></a> </div> </div> <div class="codebox__code" data-code="1"> <pre class="line-numbers language-javascript"><code>alert(1n + 2n); // 3 alert(5n / 2n); // 2</code></pre> </div> </div> </div><p>注意: 除算 <code>5/2</code> は小数部分なしでゼロに向かって丸められた結果を返します。すべての bigint に対する操作は bigint を返します。</p> <p>bigint と通常の数値を混在させることはできません:</p> <div id="s8x748fly8" data-trusted="1" class="code-example"> <div class="codebox code-example__codebox"> <div class="toolbar codebox__toolbar"> <div class="toolbar__tool"> <a href="#" title="実行" data-action="run" class="toolbar__button toolbar__button_run"></a> </div> <div class="toolbar__tool"> <a href="#" title="サンドボックで開く" target="_blank" data-action="edit" class="toolbar__button toolbar__button_edit"></a> </div> </div> <div class="codebox__code" data-code="1"> <pre class="line-numbers language-javascript"><code>alert(1n + 2); // Error: BigInt と他の型を混ぜることはできません</code></pre> </div> </div> </div><p>必要なら明示的な変換が必要です: 次のように <code>BigInt()</code> か <code>Number()</code> を利用します:</p> <div id="86lk5qa1hx" data-trusted="1" class="code-example"> <div class="codebox code-example__codebox"> <div class="toolbar codebox__toolbar"> <div class="toolbar__tool"> <a href="#" title="実行" data-action="run" class="toolbar__button toolbar__button_run"></a> </div> <div class="toolbar__tool"> <a href="#" title="サンドボックで開く" target="_blank" data-action="edit" class="toolbar__button toolbar__button_edit"></a> </div> </div> <div class="codebox__code" data-code="1"> <pre class="line-numbers language-javascript"><code>let bigint = 1n; let number = 2; // number から bigint へ alert(bigint + BigInt(number)); // 3 // bigint から number へ alert(Number(bigint) + number); // 3</code></pre> </div> </div> </div><p>変換操作は常に粛々と行われ、決してエラーになりません。が、bigint が大きすぎて数値型にフィットしない場合、余分なビットが切り捨てられるため、このような変換には注意が必要です。</p> <div class="important important_smart"> <div class="important__header"><span class="important__type">bigint では単項プラスはサポートされていません。</span></div> <div class="important__content"><p>単項プラス演算子 <code>+value</code> は <code>value</code> を数値に変換するためのよく知られた方法です。</p> <p>混乱を避けるため、bigint ではサポートされていません:</p> <div id="jymeqabqnf" data-trusted="1" class="code-example"> <div class="codebox code-example__codebox"> <div class="toolbar codebox__toolbar"> <div class="toolbar__tool"> <a href="#" title="実行" data-action="run" class="toolbar__button toolbar__button_run"></a> </div> <div class="toolbar__tool"> <a href="#" title="サンドボックで開く" target="_blank" data-action="edit" class="toolbar__button toolbar__button_edit"></a> </div> </div> <div class="codebox__code" data-code="1"> <pre class="line-numbers language-javascript"><code>let bigint = 1n; alert( +bigint ); // error</code></pre> </div> </div> </div><p>したがって、bigint を数値に変換する場合には <code>Number()</code> を使用してください。</p> </div></div> <h2><a class="main__anchor" name="ref-704" href="#ref-704">比較</a></h2><p><code><</code>, <code>></code> のような比較は bigint と数値でうまく機能します:</p> <div id="yywh198h3k" data-trusted="1" class="code-example"> <div class="codebox code-example__codebox"> <div class="toolbar codebox__toolbar"> <div class="toolbar__tool"> <a href="#" title="実行" data-action="run" class="toolbar__button toolbar__button_run"></a> </div> <div class="toolbar__tool"> <a href="#" title="サンドボックで開く" target="_blank" data-action="edit" class="toolbar__button toolbar__button_edit"></a> </div> </div> <div class="codebox__code" data-code="1"> <pre class="line-numbers language-javascript"><code>alert( 2n > 1n ); // true alert( 2n > 1 ); // true</code></pre> </div> </div> </div><p>ですが注意してください。数値と bigint は異なる型なので、等価 <code>==</code> にはなりますが、厳密等価 <code>===</code> にはなりません。</p> <div id="zaoxio2w10" data-trusted="1" class="code-example"> <div class="codebox code-example__codebox"> <div class="toolbar codebox__toolbar"> <div class="toolbar__tool"> <a href="#" title="実行" data-action="run" class="toolbar__button toolbar__button_run"></a> </div> <div class="toolbar__tool"> <a href="#" title="サンドボックで開く" target="_blank" data-action="edit" class="toolbar__button toolbar__button_edit"></a> </div> </div> <div class="codebox__code" data-code="1"> <pre class="line-numbers language-javascript"><code>alert( 1 == 1n ); // true alert( 1 === 1n ); // false</code></pre> </div> </div> </div><h2><a class="main__anchor" name="ref-705" href="#ref-705">Boolean 操作</a></h2><p><code>if</code> や他の boolean 操作内では、bigint は数値のように振る舞います。</p> <p>例えば、<code>if</code> では bigint <code>0n</code> は偽であり、他の値は真です:</p> <div id="zp19dcryp7" data-trusted="1" class="code-example"> <div class="codebox code-example__codebox"> <div class="toolbar codebox__toolbar"> <div class="toolbar__tool"> <a href="#" title="実行" data-action="run" class="toolbar__button toolbar__button_run"></a> </div> <div class="toolbar__tool"> <a href="#" title="サンドボックで開く" target="_blank" data-action="edit" class="toolbar__button toolbar__button_edit"></a> </div> </div> <div class="codebox__code" data-code="1"> <pre class="line-numbers language-javascript"><code>if (0n) { // 実行されることはありません }</code></pre> </div> </div> </div><p>bigint を利用した <code>||</code>, <code>&&</code> などの boolean 操作も数値と同じように動作します:</p> <div id="0qlfh7bgj4" data-trusted="1" class="code-example"> <div class="codebox code-example__codebox"> <div class="toolbar codebox__toolbar"> <div class="toolbar__tool"> <a href="#" title="実行" data-action="run" class="toolbar__button toolbar__button_run"></a> </div> <div class="toolbar__tool"> <a href="#" title="サンドボックで開く" target="_blank" data-action="edit" class="toolbar__button toolbar__button_edit"></a> </div> </div> <div class="codebox__code" data-code="1"> <pre class="line-numbers language-javascript"><code>alert( 1n || 2 ); // 1 (1n は真とみなされます) alert( 0n || 2 ); // 2 (0n は偽とみなされます)</code></pre> </div> </div> </div><h2><a class="main__anchor" name="ref-706" href="#ref-706">Polyfills</a></h2><p>bigint のポリフィルには注意が必要です。理由は <code>+</code>, <code>-</code> などの多くの JavaScript 演算子は通常の数値の場合と比較して、bigint での動作は異なるためです。</p> <p>例えば、bigint の除算は常に bigint を返します（必要に応じて丸められます）。</p> <p>このような振る舞いをエミュレートするために、ポリフィルはコードを分析し、そのようなすべての演算子をその関数に置き換える必要があります。ですが、それをするのは面倒であり、多くのパフォーマンスコストがかかります。</p> <p>そのため、よく知られている、良いポリフィルはありません。</p> <p>ですが、その逆は <a href="https://github.com/GoogleChromeLabs/jsbi">JSBI</a> ライブラリの開発者により提案されています。</p> <p>このライブラリは独自のメソッドを使用して大きな数字を実装しています。我々は、ネイティブの bigint の代わりにこれが利用できます:</p> <table> <thead> <tr> <th>操作</th> <th>ネイティブ <code>BigInt</code></th> <th>JSBI</th> </tr> </thead> <tbody> <tr> <td>数値から作成</td> <td><code>a = BigInt(789)</code></td> <td><code>a = JSBI.BigInt(789)</code></td> </tr> <tr> <td>足し算</td> <td><code>c = a + b</code></td> <td><code>c = JSBI.add(a, b)</code></td> </tr> <tr> <td>引き算</td> <td><code>c = a - b</code></td> <td><code>c = JSBI.subtract(a, b)</code></td> </tr> <tr> <td>…</td> <td>…</td> <td>…</td> </tr> </tbody> </table> <p>…そしてポリフィル(Babelプラグイン)を使用して、JSBI呼び出しをブラウザがサポートしているネイティブ bigint に変換します。</p> <p>つまり、このアプローチはネイティブの bigint の代わりに JSBI でコードを書くことを提案しています。しかし、JSBI は内部的には bigint と同じように数値を処理し、仕様にしがたってエミュレートするので、このコードは “bigint対応” になります。</p> <p>このようなJSBIコードは、bigintをサポートしていないエンジンとサポートしているエンジンに “そのまま” 使用できます。ポリフィルは、呼び出しをネイティブbigintに変換します。</p> <h2><a class="main__anchor" name="ref-707" href="#ref-707">参照</a></h2><ul> <li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt">MDN docs on BigInt</a>.</li> <li><a href="https://tc39.es/ecma262/#sec-bigint-objects">Specification</a>.</li> </ul> </div></article></div><div class="page__nav-wrap"><a class="page__nav page__nav_prev" href="/reference-type" data-tooltip="参照型"><span class="page__nav-text"><span class="page__nav-text-shortcut"></span></span><span class="page__nav-text-alternate">前のレッスン</span></a><a class="page__nav page__nav_next" href="/ui" data-tooltip="ブラウザ: ドキュメント, イベント, インタフェース"><span class="page__nav-text"><span class="page__nav-text-shortcut"></span></span><span class="page__nav-text-alternate">次のレッスン</span></a></div><div class="article-tablet-foot tablet-only"><div class="article-tablet-foot__layout"><div class="share-icons"><span class="share-icons__title">シェア</span><a class="share share_tw" href="https://twitter.com/share?url=https%3A%2F%2Fja.javascript.info%2Fbigint" rel="nofollow"></a><a class="share share_fb" href="https://www.facebook.com/sharer/sharer.php?s=100&p%5Burl%5D=https%3A%2F%2Fja.javascript.info%2Fbigint" rel="nofollow"></a></div><div class="article-tablet-foot__map"><a class="map" href="/tutorial/map" data-action="tutorial-map"><span class="map__text">チュートリアルマップ</span></a></div></div></div><div class="comments formatted" id="comments"><div class="comments__header"><h2 class="comments__header-title"><a href="#comments" name="comments">コメント</a></h2><div class="comments__read-before"><span class="comments__read-before-link">コメントをする前に読んでください…</span><div class="comments__read-before-popup"><div class="comments__read-before-popup-i"><ul><li>自由に記事への追加や質問を投稿をしたり、それらに回答してください。</li><li>数語のコードを挿入するには、<code><code></code> タグを使ってください。複数行の場合は <code><pre></code> を、10行を超える場合にはサンドボックスを使ってください(<a href='https://plnkr.co/edit/?p=preview'>plnkr</a>, <a href='https://jsbin.com'>JSBin</a>, <a href='http://codepen.io'>codepen</a>…)。</li><li>記事の中で理解できないことがあれば、詳しく説明してください。</li></ul></div></div></div></div><div id="disqus_thread"></div><script>var disqus_config = function() { if (!this.page) this.page = {}; 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