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---
title: Math.clz32()
slug: Web/JavaScript/Reference/Global_Objects/Math/clz32
tags:
- ECMAScript 2015
- Java
- Math
- Method
- Reference
translation_of: Web/JavaScript/Reference/Global_Objects/Math/clz32
---
<div>{{JSRef}}</div>
<p>Die <strong><code>Math.clz32()</code></strong> Funktion zählt die führenden Nullbits in der 32-Bit binär Repräsentation einer Nummer.</p>
<div>{{EmbedInteractiveExample("pages/js/math-clz32.html")}}</div>
<h2 id="Syntax">Syntax</h2>
<pre class="syntaxbox"><code>Math.clz32(<var>x</var>)</code></pre>
<h3 id="Parameter">Parameter</h3>
<dl>
<dt><code>x</code></dt>
<dd>Eine Nummer.</dd>
</dl>
<h3 id="Rückgabewert">Rückgabewert</h3>
<p>Die Anzahl der führenden Nullbits in der 32-Bit binör Repräsentation der übergebenen Zahl.</p>
<h2 id="Beschreibung">Beschreibung</h2>
<p>"<code>clz32</code>" steht für <code>CountLeadingZeroes32 (<em>AnzahlFührenderNullen32</em>)</code>.</p>
<p>Wenn <code>x</code> keine Nummer ist, wird <code>x</code> in eine Nummer konvertiert. Danach wird diese Nummer in einen 32-Bit vorzeichenlose Ganzzahl (unsigned integer) konvertiert.</p>
<p>Wenn die konvertierte 32-Bit vorzeichenlose Zahl <code>0</code> ist, so wird die Funktion 32 zurück geben, weil alle Bits <code>0</code> sind.</p>
<p>Diese Funktion ist nützlich für Systeme, die in zu JavaScript kompilieren (z. B. <a href="/en-US/docs/Emscripten">Emscripten</a>).</p>
<h2 id="Beispiele">Beispiele</h2>
<h3 id="Einsatz_von_Math.clz32()">Einsatz von <code>Math.clz32()</code></h3>
<pre class="brush: js">Math.clz32(1); // 31
Math.clz32(1000); // 22
Math.clz32(); // 32
[NaN, Infinity, -Infinity, 0, -0, null, undefined, 'foo', {}, []].filter(
function(n) {
return Math.clz32(n) !== 32
}); // []
Math.clz32(true); // 31
Math.clz32(3.5); // 30
</pre>
<h2 id="Polyfill">Polyfill</h2>
<p>Der folgende Polyfill ist der effizienteste.</p>
<pre class="brush: js line-numbers language-js"><code class="language-js"><span class="keyword token">if</span> <span class="punctuation token">(</span><span class="operator token">!</span>Math<span class="punctuation token">.</span>clz32<span class="punctuation token">)</span> <span class="punctuation token">{</span>
Math<span class="punctuation token">.</span>clz32 <span class="operator token">=</span> <span class="keyword token">function</span><span class="punctuation token">(</span>x<span class="punctuation token">)</span> <span class="punctuation token">{</span>
<span class="comment token">// Let n be ToUint32(x).</span>
<span class="comment token">// Let p be the number of leading zero bits in </span>
<span class="comment token">// the 32-bit binary representation of n.</span>
<span class="comment token">// Return p. </span>
<span class="keyword token">if</span> <span class="punctuation token">(</span>x <span class="operator token">==</span> <span class="keyword token">null</span> <span class="operator token">||</span> x <span class="operator token">===</span> <span class="number token">0</span><span class="punctuation token">)</span> <span class="punctuation token">{</span>
<span class="keyword token">return</span> <span class="number token">32</span><span class="punctuation token">;</span>
<span class="punctuation token">}</span>
<span class="keyword token">return</span> <span class="number token">31</span> <span class="operator token">-</span> Math<span class="punctuation token">.</span><span class="function token">floor</span><span class="punctuation token">(</span>Math<span class="punctuation token">.</span><span class="function token">log</span><span class="punctuation token">(</span>x <span class="operator token">></span><span class="operator token">></span><span class="operator token">></span> <span class="number token">0</span><span class="punctuation token">)</span> <span class="operator token">*</span> Math<span class="punctuation token">.</span>LOG2E<span class="punctuation token">)</span><span class="punctuation token">;</span>
<span class="punctuation token">}</span><span class="punctuation token">;</span>
<span class="punctuation token">}</span></code></pre>
<h2 id="Spezifikationen">Spezifikationen</h2>
<table class="standard-table">
<tbody>
<tr>
<th scope="col">Specification</th>
<th scope="col">Status</th>
<th scope="col">Comment</th>
</tr>
<tr>
<td>{{SpecName('ES2015', '#sec-math.clz32', 'Math.clz32')}}</td>
<td>{{Spec2('ES2015')}}</td>
<td>Initiale Definition.</td>
</tr>
<tr>
<td>{{SpecName('ESDraft', '#sec-math.clz32', 'Math.clz32')}}</td>
<td>{{Spec2('ESDraft')}}</td>
<td> </td>
</tr>
</tbody>
</table>
<h2 id="Browserkompatibilität">Browserkompatibilität</h2>
<p class="hidden">The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out <a href="https://github.com/mdn/browser-compat-data">https://github.com/mdn/browser-compat-data</a> and send us a pull request.</p>
<p>{{Compat("javascript.builtins.Math.clz32")}}</p>
<h2 id="Siehe_auch">Siehe auch</h2>
<ul>
<li>{{jsxref("Math")}}</li>
<li>{{jsxref("Math.imul")}}</li>
</ul>
|
