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• 构造函数
• 特性
• 方法
• 范例
• 规范
• 浏览器兼容性
• 相关话题

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。

WritableStreamDefaultWriter 接口的 Streams API is the object returned by WritableStream.getWriter() and once created locks the writer to the WritableStream ensuring that no other streams can write to the underlying sink.

构造函数

WritableStreamDefaultWriter()

创建新的 WritableStreamDefaultWriter 对象实例。

特性

WritableStreamDefaultWriter.closed 只读

Allows you to write code that responds to an end to the streaming process. Returns a promise that fulfills if the stream becomes closed or the writer's lock is released, or rejects if the stream errors.

WritableStreamDefaultWriter.desiredSize 只读

Returns the desired size required to fill the stream's internal queue.

WritableStreamDefaultWriter.ready 只读

返回 Promise that resolves when the desired size of the stream's internal queue transitions from non-positive to positive, signaling that it is no longer applying backpressure.

方法

WritableStreamDefaultWriter.abort()

Aborts the stream, signaling that the producer can no longer successfully write to the stream and it is to be immediately moved to an error state, with any queued writes discarded.

WritableStreamDefaultWriter.close()

Closes the associated writable stream.

WritableStreamDefaultWriter.releaseLock()

Releases the writer's lock on the corresponding stream. After the lock is released, the writer is no longer active. If the associated stream is errored when the lock is released, the writer will appear errored in the same way from now on; otherwise, the writer will appear closed.

WritableStreamDefaultWriter.write()

Writes a passed chunk of data to a WritableStream and its underlying sink, then returns a Promise that resolves to indicate the success or failure of the write operation.

范例

The following example shows the creation of a 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 'WritableStreamDefaultWriter' 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
WritableStreamDefaultWriter	Chrome 59	Edge 16	Firefox No	IE No	Opera 46	Safari ?	WebView Android 59	Chrome Android 59	Firefox Android No	Opera Android 43	Safari iOS ?	Samsung Internet Android 7.0
WritableStreamDefaultWriter() 构造函数	Chrome 59	Edge 16	Firefox No	IE No	Opera 46	Safari ?	WebView Android 59	Chrome Android 59	Firefox Android No	Opera Android 43	Safari iOS ?	Samsung Internet Android 7.0
abort	Chrome 59	Edge 16	Firefox No	IE No	Opera 46	Safari ?	WebView Android 59	Chrome Android 59	Firefox Android No	Opera Android 43	Safari iOS ?	Samsung Internet Android 7.0
close	Chrome 59	Edge 16	Firefox No	IE No	Opera 46	Safari ?	WebView Android 59	Chrome Android 59	Firefox Android No	Opera Android 43	Safari iOS ?	Samsung Internet Android 7.0
closed	Chrome 59	Edge 16	Firefox No	IE No	Opera 46	Safari ?	WebView Android 59	Chrome Android 59	Firefox Android No	Opera Android 43	Safari iOS ?	Samsung Internet Android 7.0
desiredSize	Chrome 59	Edge 16	Firefox No	IE No	Opera 46	Safari ?	WebView Android 59	Chrome Android 59	Firefox Android No	Opera Android 43	Safari iOS ?	Samsung Internet Android 7.0
ready	Chrome 59	Edge 16	Firefox No	IE No	Opera 46	Safari ?	WebView Android 59	Chrome Android 59	Firefox Android No	Opera Android 43	Safari iOS ?	Samsung Internet Android 7.0
releaseLock	Chrome 59	Edge 16	Firefox No	IE No	Opera 46	Safari ?	WebView Android 59	Chrome Android 59	Firefox Android No	Opera Android 43	Safari iOS ?	Samsung Internet Android 7.0
write	Chrome 59	Edge 16	Firefox No	IE No	Opera 46	Safari ?	WebView Android 59	Chrome Android 59	Firefox Android No	Opera Android 43	Safari iOS ?	Samsung Internet Android 7.0

图例

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完整支持

不支持

不支持

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实验。期望将来行为有所改变。

实验。期望将来行为有所改变。

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