WritableStreamDefaultWriter.ready

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since June 2022.

WritableStreamDefaultWriter 接口的只读属性 ready 返回一个 Promise，当流填充内部队列的所需大小从非正数变为正数时兑现，表明它不再应用背压。

值

一个 Promise。

示例

以下示例使用了 ready 属性的两种用法。第一种使用 ready 来确保 WritableStream 已完成写入，因此能够保证其已经准备好接收新的数据。第二种也检查 WritableStream 是否完成写入，但是这一次是因为写入操作必须在 writer 关闭之前完成。

js
function sendMessage(message, writableStream) {
  // defaultWriter is of type WritableStreamDefaultWriter
  var defaultWriter = writableStream.getWriter();
  var encoder = new TextEncoder();
  var encoded = encoder.encode(message, { stream: true });
  encoded.forEach(function (chunk) {
    // Make sure the stream and its writer are able to
    //   receive data.
    defaultWriter.ready.then(function () {
      defaultWriter
        .write(chunk)
        .then(function () {
          console.log("Chunk written to sink.");
        })
        .catch(function (err) {
          console.log("Chunk error: " + err);
        });
    });
    // Call ready again to ensure that all chunks are written
    //   before closing the writer.
    defaultWriter.ready.then(function () {
      defaultWriter
        .close()
        .then(function () {
          console.log("All chunks written");
        })
        .catch(function (err) {
          console.log("Stream error: " + err);
        });
    });
  });
}

规范

Specification
Streams
# ref-for-default-writer-ready⑨

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