WritableStream.getWriter()

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范例
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草案
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这是实验性技术
检查浏览器兼容性表格要小心谨慎在生产中使用这之前。

getWriter() 方法在 WritableStream interface returns a new instance of WritableStreamDefaultWriter and locks the stream to that instance. While the stream is locked, no other writer can be acquired until this one is released.

句法

var writer = writableStream.getWriter();

参数

None.

返回值

A WritableStreamDefaultWriter 对象实例。

异常

TypeError: The stream you are trying to create a writer for is not a WritableStream .

范例

The following example illustrates several features of this interface. It shows the creation of the WritableStream with a custom sink and an API-supplied queuing strategy. It then calls a function called sendMessage() , passing the newly created stream and a string. Inside this function it calls the stream's getWriter() method, which returns an instance of WritableStreamDefaultWriter 。 forEach() call is used to write each chunk of the string to the stream. Finally, write() and close() return promises that are processed to deal with success or failure of chunks and streams.

const list = document.querySelector('ul');
function sendMessage(message, writableStream) {
  // defaultWriter is of type WritableStreamDefaultWriter
  const defaultWriter = writableStream.getWriter();
  const encoder = new TextEncoder();
  const encoded = encoder.encode(message, { stream: true });
  encoded.forEach((chunk) => {
    defaultWriter.ready
      .then(() => {
        return defaultWriter.write(chunk);
      })
      .then(() => {
        console.log("Chunk written to sink.");
      })
      .catch((err) => {
        console.log("Chunk error:", err);
      });
  });
  // Call ready again to ensure that all chunks are written
  //   before closing the writer.
  defaultWriter.ready
    .then(() => {
      defaultWriter.close();
    })
    .then(() => {
      console.log("All chunks written");
    })
    .catch((err) => {
      console.log("Stream error:", err);
    });
}
const decoder = new TextDecoder("utf-8");
const queuingStrategy = new CountQueuingStrategy({ highWaterMark: 1 });
let result = "";
const writableStream = new WritableStream({
  // Implement the sink
  write(chunk) {
    return new Promise((resolve, reject) => {
      var buffer = new ArrayBuffer(2);
      var view = new Uint16Array(buffer);
      view[0] = chunk;
      var decoded = decoder.decode(view, { stream: true });
      var listItem = document.createElement('li');
      listItem.textContent = "Chunk decoded: " + decoded;
      list.appendChild(listItem);
      result += decoded;
      resolve();
    });
  },
  close() {
    var listItem = document.createElement('li');
    listItem.textContent = "[MESSAGE RECEIVED] " + result;
    list.appendChild(listItem);
  },
  abort(err) {
    console.log("Sink error:", err);
  }
}, queuingStrategy);
sendMessage("Hello, world.", writableStream);

You can find the full code in our Simple writer example .

规范

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

浏览器兼容性

The compatibility table in 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
`getWriter`	Chrome 59	Edge 16	Firefox No	IE No	Opera 47	Safari ?	WebView Android 59	Chrome Android 59	Firefox Android No	Opera Android 44	Safari iOS ?	Samsung Internet Android 7.0

图例

完整支持
不支持
兼容性未知 ?
实验。期望将来行为有所改变。

元数据

最后修改： Feb 11, 2020

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句法

参数

返回值

异常

范例

规范

浏览器兼容性

图例

相关话题