---
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>

{{Compat("api.AnalyserNode.getByteFrequencyData")}}

<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>