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• 句法
• 范例
• 规范
• 浏览器兼容性
• 相关话题

getReader() 方法在 ReadableStream interface creates a reader and locks the stream to it. While the stream is locked, no other reader can be acquired until this one is released.

句法

var reader = readableStream.getReader({mode});
					

参数

{mode} 可选

An object containing a property mode , which takes as its value a DOMString specifying the type of reader to create.  Values can be:

• "byob" , which results in a ReadableStreamBYOBReader being created that can read readable byte streams (i.e. can handle "bring your own buffer" reading).
• undefined (or not specified at all — this is the default), which results in a ReadableStreamDefaultReader being created that can read individual chunks from a stream.

返回值

A ReadableStreamDefaultReader or ReadableStreamBYOBReader object instance, depending on the mode 值。

异常

RangeError

The provided mode value is not "byob" or undefined .

TypeError

The stream you are trying to create a reader for is not a ReadableStream .

范例

In the following simple example, a previously-created custom ReadableStream is read using a ReadableStreamDefaultReader created using getReader() . (see our Simple random stream example for the full code). Each chunk is read sequentially and output to the UI, until the stream has finished being read, at which point we return out of the recursive function and print the entire stream to another part of the UI.

function fetchStream() {
  const reader = stream.getReader();
  let charsReceived = 0;
  // read() returns a promise that resolves
  // when a value has been received
  reader.read().then(function processText({ done, value }) {
    // Result objects contain two properties:
    // done  - true if the stream has already given you all its data.
    // value - some data. Always undefined when done is true.
    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;
    // Read some more, and call this function again
    return reader.read().then(processText);
  });
}
					

规范

规范	状态	注释
流 The definition of 'getReader()' in that specification.	实时标准	初始定义。

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

更新 GitHub 上的兼容性数据

	桌面						移动
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
getReader	Chrome 43	Edge 14	Firefox 65 65 57 Disabled Disabled From version 57: this feature is behind the dom.streams.enabled preference (needs to be set to true ) 和 preference (needs to be set to ). To change preferences in Firefox, visit about:config.	IE No	Opera 30	Safari 10.1	WebView Android 43	Chrome Android 43	Firefox Android 65 65 57 Disabled Disabled From version 57: this feature is behind the dom.streams.enabled preference (needs to be set to true ) 和 preference (needs to be set to ). To change preferences in Firefox, visit about:config.	Opera Android 30	Safari iOS 10.3	Samsung Internet Android 4.0

图例

完整支持

完整支持

不支持

不支持

实验。期望将来行为有所改变。

实验。期望将来行为有所改变。

用户必须明确启用此特征。

用户必须明确启用此特征。

元数据

• 最后修改： Jan 3, 2020

相关话题

1. Streams API
2. ReadableStream
3. 构造函数

   1. ReadableStream()
4. 特性

   1. locked
5. 方法

   1. cancel()
   2. getReader()
   3. pipeThrough()
   4. pipeTo()
   5. tee()
6. Related pages for Streams

   1. Body.body
   2. ByteLengthQueuingStrategy
   3. CountQueuingStrategy
   4. ReadableByteStreamController
   5. ReadableStreamBYOBReader
   6. ReadableStreamBYOBRequest
   7. ReadableStreamDefaultController
   8. ReadableStreamDefaultReader
   9. WindowOrWorkerGlobalScope.fetch()
   10. WritableStream
   11. WritableStreamDefaultController
   12. WritableStreamDefaultWriter