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author | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:40:17 -0500 |
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committer | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:40:17 -0500 |
commit | 33058f2b292b3a581333bdfb21b8f671898c5060 (patch) | |
tree | 51c3e392513ec574331b2d3f85c394445ea803c6 /files/zh-cn/web/api/readablestream/getreader | |
parent | 8b66d724f7caf0157093fb09cfec8fbd0c6ad50a (diff) | |
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Diffstat (limited to 'files/zh-cn/web/api/readablestream/getreader')
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diff --git a/files/zh-cn/web/api/readablestream/getreader/index.html b/files/zh-cn/web/api/readablestream/getreader/index.html new file mode 100644 index 0000000000..bddbcf0bae --- /dev/null +++ b/files/zh-cn/web/api/readablestream/getreader/index.html @@ -0,0 +1,103 @@ +--- +title: ReadableStream.getReader() +slug: Web/API/ReadableStream/getReader +tags: + - API + - getReader + - 参考 + - 可读取流 + - 方法 + - 流 +translation_of: Web/API/ReadableStream/getReader +--- +<div>{{APIRef("Streams")}}</div> + +<p class="summary">使用{{domxref("ReadableStream")}}接口的<strong><code>getReader()</code></strong> 方法创建一个<code>reader</code>,并将流锁定。只有当前<code>reader</code>将流释放后,其他<code>reader</code>才能使用。</p> + +<h2 id="语法">语法</h2> + +<pre class="syntaxbox notranslate">var reader = readableStreamInstance.getReader(<em>{mode}</em>);</pre> + +<h3 id="参数">参数</h3> + +<dl> + <dt>{mode}- 可选参数</dt> + <dd>具有 <code>mode</code>参数的对象,值为 {{domxref("DOMString")}}类型 ,用来指定要创建的阅读器的类型。其值可以是: + <ul> + <li><code>byob</code>, 结果为 {{domxref("ReadableStreamBYOBReader")}} 类型,可读取可读字节流。</li> + <li><code>undefined</code> (未定类型 — 默认值), 返回{{domxref("ReadableStreamDefaultReader")}} ,可以从流中返回单个块。</li> + </ul> + </dd> +</dl> + +<h3 id="返回值">返回值</h3> + +<p>{{domxref("ReadableStreamDefaultReader")}} 类型或{{domxref("ReadableStreamBYOBReader")}} 类型 实例, 取决于 <code>mode</code> 值.</p> + +<h3 id="错误">错误</h3> + +<dl> + <dt>RangeError——范围错误</dt> + <dd>提供的 mode值 既不是 <font face="consolas, Liberation Mono, courier, monospace"><span style="background-color: rgba(220, 220, 220, 0.5);">byob</span></font>也不是 <font face="consolas, Liberation Mono, courier, monospace"><span style="background-color: rgba(220, 220, 220, 0.5);">undefined</span></font></dd> + <dt>TypeError——类型错误</dt> + <dd>尝试创建阅读器的流不是 {{domxref("ReadableStream")}}类型</dd> +</dl> + +<h2 id="例子">例子</h2> + +<p>下面是个简单的例子, 在读取<code>ReadableStream</code>前,使用 <code>getReader()</code>创建一个{{domxref("ReadableStreamDefaultReader")}} 。(查看全部代码 <a href="https://mdn.github.io/dom-examples/streams/simple-random-stream/">Simple random stream example</a> ). 按顺序读取每个块,并传递给UI, 当整个流被读取完毕后, 从递归方法中退出,并在UI的另一部分输出整个流。</p> + +<pre class="brush: js notranslate">function fetchStream() { + const reader = stream.getReader(); + let charsReceived = 0; + + // read() 返回了一个promise + // 当数据被接收时resolve + reader.read().then(function processText({ done, value }) { + // Result对象包含了两个属性: + // done - 当stream传完所有数据时则变成true + // value - 数据片段。当done不为true时永远为undefined + if (done) { + console.log("Stream complete"); + para.textContent = value; + return; + } + + // value for fetch streams is a Uint8Array + charsReceived += value.length; + const chunk = value; + let listItem = document.createElement('li'); + listItem.textContent = 'Received ' + charsReceived + ' characters so far. Current chunk = ' + chunk; + list2.appendChild(listItem); + + result += chunk; + + // 再次调用这个函数以读取更多数据 + return reader.read().then(processText); + }); +}</pre> + +<h2 id="说明">说明</h2> + +<table class="standard-table"> + <tbody> + <tr> + <th scope="col">Specification</th> + <th scope="col">Status(状态)</th> + <th scope="col">Comment(备注)</th> + </tr> + <tr> + <td>{{SpecName("Streams","#rs-get-reader","getReader()")}}</td> + <td>{{Spec2('Streams')}}</td> + <td>Initial definition.</td> + </tr> + </tbody> +</table> + +<h2 id="浏览器兼容">浏览器兼容</h2> + +<div class="hidden"> +<p>The compatibility table on 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> +</div> + +<p>{{Compat("api.ReadableStream.getReader")}}</p> |