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+---
+title: 加算 (+)
+slug: Web/JavaScript/Reference/Operators/Addition
+tags:
+  - JavaScript
+  - Language feature
+  - Operator
+  - Reference
+translation_of: Web/JavaScript/Reference/Operators/Addition
+---
+<div>{{jsSidebar("Operators")}}</div>
+
+<p>加算演算子 (<code>+</code>) は、数値オペランドまたは文字列連結の合計を生成します。</p>
+
+<div>{{EmbedInteractiveExample("pages/js/expressions-addition.html")}}</div>
+
+<div></div>
+
+
+
+<h2 id="構文">構文</h2>
+
+<pre class="syntaxbox notranslate"><strong>Operator:</strong> <var>x</var> + <var>y</var>
+</pre>
+
+<h2 id="例">例</h2>
+
+<h3 id="数値加算">数値加算</h3>
+
+<pre class="brush: js notranslate">// 数値 + 数値 -&gt; 加算
+1 + 2 // 3
+
+// ブール値 + 数値 -&gt; 加算
+true + 1 // 2
+
+// ブール値 + ブール値 -&gt; 加算
+false + false // 0
+</pre>
+
+<h3 id="文字列連結">文字列連結</h3>
+
+<pre class="brush: js notranslate">// 文字列 + 文字列 -&gt; 連結
+'foo' + 'bar' // "foobar"
+
+// 数値 + 文字列 -&gt; 連結
+5 + 'foo' // "5foo"
+
+// 文字列 + ブール値 -&gt; 連結
+'foo' + false // "foofalse"</pre>
+
+<h2 id="仕様">仕様</h2>
+
+<table class="standard-table">
+ <tbody>
+  <tr>
+   <th scope="col">仕様</th>
+  </tr>
+  <tr>
+   <td>{{SpecName('ESDraft', '#sec-addition-operator-plus', 'Addition operator')}}</td>
+  </tr>
+ </tbody>
+</table>
+
+<h2 id="ブラウザーの互換性">ブラウザーの互換性</h2>
+
+
+
+<p>{{Compat("javascript.operators.addition")}}</p>
+
+<h2 id="関連項目">関連項目</h2>
+
+<ul>
+ <li><a href="https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Operators/Subtraction">減算演算子</a></li>
+ <li><a href="https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Operators/Division">除算演算子</a></li>
+ <li><a href="https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Operators/Multiplication">乗算演算子</a></li>
+ <li><a href="https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Operators/Remainder">剰余演算子</a></li>
+ <li><a href="https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Operators/Exponentiation">べき乗演算子</a></li>
+ <li><a href="https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Operators/Increment">インクリメント演算子</a></li>
+ <li><a href="https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Operators/Decrement">デクリメント演算子</a></li>
+ <li><a href="https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Operators/Unary_negation">単項マイナス演算子</a></li>
+ <li><a href="https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Operators/Unary_plus">単項プラス演算子</a></li>
+</ul>