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+---
+title: Boolean
+slug: Web/JavaScript/Reference/Global_Objects/Boolean
+translation_of: Web/JavaScript/Reference/Global_Objects/Boolean
+---
+<div>{{JSRef}}</div>
+
+<p><strong><code>Boolean</code></strong> 是布林值的包覆器。</p>
+
+<h2 id="語法">語法</h2>
+
+<pre class="syntaxbox">new Boolean([<var>value</var>])</pre>
+
+<h3 id="參數">參數</h3>
+
+<dl>
+ <dt><code>value</code> {{optional_inline}}</dt>
+ <dd>這個<code>Boolean</code>物件的初始值。</dd>
+</dl>
+
+<h2 id="說明">說明</h2>
+
+<p>傳入的第一個參數值,如果需要的話,會被轉換成布林值。如果沒傳值,或者是<code>0</code>、<code>-0</code>、{{jsxref("null")}}、<code>false</code>、{{jsxref("NaN")}}、{{jsxref("undefined")}}、空字串(<code>""</code>)的話,這個物件的值會被初始化成<code>false</code>。大多數情況下,DOM 物件 {{domxref("document.all")}} 被傳入後,也會將其初始化為<code>false</code>。至於其他的值,包含所有物件或<code>"false"</code>字串,都會使其初始化為<code>true</code>。</p>
+
+<p>不要將原始型別的布林值和這個布林物件搞混,它們並不相同。</p>
+
+<p>在判斷式中,任何物件只要不是 {{jsxref("undefined")}} 或 {{jsxref("null")}} ,儘管是值為<code>false</code> 的 <code>Boolean</code> 物件,都會被轉換成<code>true</code>。舉例來說,下列的 {{jsxref("Statements/if...else", "if")}} 判斷式中的布林值即為<code>true</code>:</p>
+
+<pre class="brush: js">var x = new Boolean(false);
+if (x) {
+ // this code is executed
+}
+</pre>
+
+<p>以上這個行為和<code>Boolean</code>原始型別沒有關連,反倒是下面的 {{jsxref("Statements/if...else", "if")}} 判斷式會正確地將其視為<code>false</code>:</p>
+
+<pre class="brush: js">var x = false;
+if (x) {
+ // this code is not executed
+}
+</pre>
+
+<p>不要用<code>Boolean</code>物件將非布林值轉換成布林值。反而要將<code>Boolean</code>視為函式去轉換非布林值:</p>
+
+<pre class="brush: js">var x = Boolean(expression); // 較好
+var x = new Boolean(expression); // 不要用
+</pre>
+
+<p>如果你要指定任何物件,包括值為<code>false</code>的<code>Boolean</code>物件,作為<code>Boolean</code>物件的初始值,則該<code>Boolean</code>物件的值依舊為<code>true</code>。</p>
+
+<pre class="brush: js">var myFalse = new Boolean(false); // 初始值給false,實際上為true
+var g = new Boolean(myFalse); // 想當然耳,true
+var myString = new String('Hello'); // 字串物件,'Hello'
+var s = new Boolean(myString); // 依舊為true
+</pre>
+
+<p>不要使用<code>Boolean</code>物件代替<code>Boolean</code>的原始型別!</p>
+
+<h2 id="屬性">屬性</h2>
+
+<dl>
+ <dt><code>Boolean.length</code></dt>
+ <dd>長度永遠為1。</dd>
+ <dt>{{jsxref("Boolean.prototype")}}</dt>
+ <dd>原型為<code>Boolean</code>的建構式。</dd>
+</dl>
+
+<h2 id="方法">方法</h2>
+
+<p>全域的<code>Boolean</code>物件自身沒有任何方法,它只有從原型鏈繼承而來的方法。</p>
+
+<h2 id="Boolean_實體"><code>Boolean</code> 實體</h2>
+
+<p>所有 <code>Boolean</code> 實體會繼承 {{jsxref("Boolean.prototype")}} 。和所有建構式一樣,原型物件會指派給實體那些繼承的屬性和方法。</p>
+
+<h3 id="屬性_2">屬性</h3>
+
+<div>{{page('/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean/prototype', 'Properties')}}</div>
+
+<h3 id="方法_2">方法</h3>
+
+<div>{{page('/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean/prototype', 'Methods')}}</div>
+
+<h2 id="範例">範例</h2>
+
+<h3 id="用_false_作為初始值建立_Boolean_物件">用 <code>false</code> 作為初始值建立 <code>Boolean</code> 物件</h3>
+
+<pre class="brush: js">var bNoParam = new Boolean();
+var bZero = new Boolean(0);
+var bNull = new Boolean(null);
+var bEmptyString = new Boolean('');
+var bfalse = new Boolean(false);
+</pre>
+
+<h3 id="用_true_作為初始值建立_Boolean_物件">用 <code>true</code> 作為初始值建立 <code>Boolean</code> 物件</h3>
+
+<pre class="brush: js">var btrue = new Boolean(true);
+var btrueString = new Boolean('true');
+var bfalseString = new Boolean('false');
+var bSuLin = new Boolean('Su Lin');
+var bArrayProto = new Boolean([]);
+var bObjProto = new Boolean({});
+</pre>
+
+<h2 id="規範">規範</h2>
+
+<table class="standard-table">
+ <tbody>
+ <tr>
+ <th scope="col">規範</th>
+ <th scope="col">狀態</th>
+ <th scope="col">註記</th>
+ </tr>
+ <tr>
+ <td>{{SpecName('ES1')}}</td>
+ <td>{{Spec2('ES1')}}</td>
+ <td>Initial definition. Implemented in JavaScript 1.0.</td>
+ </tr>
+ <tr>
+ <td>{{SpecName('ES5.1', '#sec-15.6', 'Boolean')}}</td>
+ <td>{{Spec2('ES5.1')}}</td>
+ <td> </td>
+ </tr>
+ <tr>
+ <td>{{SpecName('ES6', '#sec-boolean-objects', 'Boolean')}}</td>
+ <td>{{Spec2('ES6')}}</td>
+ <td> </td>
+ </tr>
+ <tr>
+ <td>{{SpecName('ESDraft', '#sec-boolean-objects', 'Boolean')}}</td>
+ <td>{{Spec2('ESDraft')}}</td>
+ <td> </td>
+ </tr>
+ </tbody>
+</table>
+
+<h2 id="瀏覽器相容性">瀏覽器相容性</h2>
+
+<div>{{CompatibilityTable}}</div>
+
+<div id="compat-desktop">
+<table class="compat-table">
+ <tbody>
+ <tr>
+ <th>Feature</th>
+ <th>Chrome</th>
+ <th>Edge</th>
+ <th>Firefox (Gecko)</th>
+ <th>Internet Explorer</th>
+ <th>Opera</th>
+ <th>Safari</th>
+ </tr>
+ <tr>
+ <td>Basic support</td>
+ <td>{{CompatVersionUnknown}}</td>
+ <td>{{CompatVersionUnknown}}</td>
+ <td>{{CompatVersionUnknown}}</td>
+ <td>{{CompatIE("6.0")}}</td>
+ <td>{{CompatVersionUnknown}}</td>
+ <td>{{CompatVersionUnknown}}</td>
+ </tr>
+ </tbody>
+</table>
+</div>
+
+<div id="compat-mobile">
+<table class="compat-table">
+ <tbody>
+ <tr>
+ <th>Feature</th>
+ <th>Android</th>
+ <th>Chrome for Android</th>
+ <th>Edge</th>
+ <th>Firefox Mobile (Gecko)</th>
+ <th>IE Mobile</th>
+ <th>Opera Mobile</th>
+ <th>Safari Mobile</th>
+ </tr>
+ <tr>
+ <td>Basic support</td>
+ <td>{{CompatVersionUnknown}}</td>
+ <td>{{CompatVersionUnknown}}</td>
+ <td>{{CompatVersionUnknown}}</td>
+ <td>{{CompatVersionUnknown}}</td>
+ <td>{{CompatVersionUnknown}}</td>
+ <td>{{CompatVersionUnknown}}</td>
+ <td>{{CompatVersionUnknown}}</td>
+ </tr>
+ </tbody>
+</table>
+</div>
+
+<h2 id="參見">參見</h2>
+
+<ul>
+ <li>{{jsxref("Boolean.prototype")}}</li>
+ <li>{{Glossary("Boolean")}}</li>
+ <li><a href="http://en.wikipedia.org/wiki/Boolean_data_type">Boolean data type (Wikipedia)</a></li>
+</ul>