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+---
+title: AnalyserNode.getByteFrequencyData()
+slug: Web/API/AnalyserNode/getByteFrequencyData
+translation_of: Web/API/AnalyserNode/getByteFrequencyData
+---
+<p>{{ APIRef("Web Audio API") }}</p>
+
+<div>
+<p>{{ domxref("AnalyserNode") }} 介面的 <strong><code>getByteFrequencyData()</code></strong> 方法會將當前的頻率資料複製到 {{domxref("Uint8Array")}} （無號 byte 陣列）。</p>
+
+<p>如果陣列的元素數目比 {{domxref("AnalyserNode.frequencyBinCount")}} 少的話，多餘的元素會被 drop 掉。如果比需要的少的話，多餘的元素會被忽略。</p>
+</div>
+
+<h2 id="語法">語法</h2>
+
+<pre class="brush: js">var audioCtx = new AudioContext();
+var analyser = audioCtx.createAnalyser();
+var dataArray = new Uint8Array(analyser.frequencyBinCount); // Uint8Array 應該要和 frequencyBinCount 等長
+analyser.getByteFrequencyData(dataArray); // 將 getByteFrequencyData() 回傳的資料放進 Uint8Array
+</pre>
+
+<h3 id="回傳值">回傳值</h3>
+
+<p>{{domxref("Uint8Array")}}。</p>
+
+<h2 id="範例">範例</h2>
+
+<p>下面的範例顯示出 {{domxref("AudioContext")}} 用於建立一個 <code>AnalyserNode</code> 的基本用法，然後 {{domxref("window.requestAnimationFrame()", "requestAnimationFrame")}} 以及 {{htmlelement("canvas")}} 用來重複收集當前聲音輸入的頻率資料並在 "winamp bargraph style" 畫出輸出。若要知道更完整的範例或是資訊，請參考 <a href="http://mdn.github.io/voice-change-o-matic/">Voice-change-O-matic</a> demo （看 <a href="https://github.com/mdn/voice-change-o-matic/blob/gh-pages/scripts/app.js#L128-L205">app.js 第 128–205 行</a> 會有相關的程式碼）。</p>
+
+<pre class="brush: js">var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
+var analyser = audioCtx.createAnalyser();
+
+  ...
+
+analyser.fftSize = 256;
+var bufferLength = analyser.frequencyBinCount;
+console.log(bufferLength);
+var dataArray = new Uint8Array(bufferLength);
+
+canvasCtx.clearRect(0, 0, WIDTH, HEIGHT);
+
+function draw() {
+  drawVisual = requestAnimationFrame(draw);
+
+  analyser.getByteFrequencyData(dataArray);
+
+  canvasCtx.fillStyle = 'rgb(0, 0, 0)';
+  canvasCtx.fillRect(0, 0, WIDTH, HEIGHT);
+
+  var barWidth = (WIDTH / bufferLength) * 2.5;
+  var barHeight;
+  var x = 0;
+
+  for(var i = 0; i &lt; bufferLength; i++) {
+    barHeight = dataArray[i];
+
+    canvasCtx.fillStyle = 'rgb(' + (barHeight+100) + ',50,50)';
+    canvasCtx.fillRect(x,HEIGHT-barHeight/2,barWidth,barHeight/2);
+
+    x += barWidth + 1;
+  }
+};
+
+draw();</pre>
+
+<h2 id="參數">參數</h2>
+
+<dl>
+ <dt>陣列</dt>
+ <dd>頻率定義域會被複製進去的 {{domxref("Uint8Array")}} 。</dd>
+</dl>
+
+<h2 id="規範">規範</h2>
+
+<table class="standard-table" style="height: 105px; width: 593px;">
+ <tbody>
+  <tr>
+   <th scope="col">規範</th>
+   <th scope="col">狀態</th>
+   <th scope="col">Comment</th>
+  </tr>
+  <tr>
+   <td>{{SpecName('Web Audio API', '#widl-AnalyserNode-getByteFrequencyData-void-Uint8Array-array', 'getByteFrequencyData()')}}</td>
+   <td>{{Spec2('Web Audio API')}}</td>
+   <td> </td>
+  </tr>
+ </tbody>
+</table>
+
+<h2 id="瀏覽器支援度">瀏覽器支援度</h2>
+
+<div>{{CompatibilityTable}}</div>
+
+<div id="compat-desktop">
+<table class="compat-table">
+ <tbody>
+  <tr>
+   <th>Feature</th>
+   <th>Chrome</th>
+   <th>Firefox (Gecko)</th>
+   <th>Internet Explorer</th>
+   <th>Opera</th>
+   <th>Safari (WebKit)</th>
+  </tr>
+  <tr>
+   <td>Basic support</td>
+   <td>{{CompatChrome(10.0)}}{{property_prefix("webkit")}}</td>
+   <td>{{CompatGeckoDesktop(25.0)}} </td>
+   <td>{{CompatNo}}</td>
+   <td>15.0{{property_prefix("webkit")}}<br>
+    22 (unprefixed)</td>
+   <td>6.0{{property_prefix("webkit")}}</td>
+  </tr>
+ </tbody>
+</table>
+</div>
+
+<div id="compat-mobile">
+<table class="compat-table">
+ <tbody>
+  <tr>
+   <th>Feature</th>
+   <th>Android</th>
+   <th>Firefox Mobile (Gecko)</th>
+   <th>Firefox OS</th>
+   <th>IE Mobile</th>
+   <th>Opera Mobile</th>
+   <th>Safari Mobile</th>
+   <th>Chrome for Android</th>
+  </tr>
+  <tr>
+   <td>Basic support</td>
+   <td>{{CompatUnknown}}</td>
+   <td>26.0</td>
+   <td>1.2</td>
+   <td>{{CompatUnknown}}</td>
+   <td>{{CompatUnknown}}</td>
+   <td>{{CompatUnknown}}</td>
+   <td>33.0</td>
+  </tr>
+ </tbody>
+</table>
+</div>
+
+<h2 id="參看">參看</h2>
+
+<ul>
+ <li><a href="/en-US/docs/Web_Audio_API/Using_Web_Audio_API">使用 Web Audio API</a></li>
+</ul>