readable.flatMap(fn[, options])

• fn <Function> | <AsyncGeneratorFunction> | <AsyncFunction> 映射流中每个块的函数。

  ¥fn <Function> | <AsyncGeneratorFunction> | <AsyncFunction> a function to map over every chunk in the stream.

  • data <any> 来自流的数据块。

    ¥data <any> a chunk of data from the stream.

  • options <Object>

    • signal <AbortSignal> 如果流被销毁则中止，允许提前中止 fn 调用。

      ¥signal <AbortSignal> aborted if the stream is destroyed allowing to abort the fn call early.

• options <Object>

  • concurrency <number> 一次调用流的 fn 的最大并发调用数。默认值：1。

    ¥concurrency <number> the maximum concurrent invocation of fn to call on the stream at once. Default: 1.

  • signal <AbortSignal> 如果信号中止，允许销毁流。

    ¥signal <AbortSignal> allows destroying the stream if the signal is aborted.

• 返回：<Readable> 是使用函数 fn 进行扁平映射的流。

  ¥Returns: <Readable> a stream flat-mapped with the function fn.

此方法通过将给定回调应用于流的每个块然后展平结果来返回新流。

¥This method returns a new stream by applying the given callback to each chunk of the stream and then flattening the result.

可以从 fn 返回流或另一个可迭代或异步可迭代，结果流将合并（展平）到返回的流中。

¥It is possible to return a stream or another iterable or async iterable from fn and the result streams will be merged (flattened) into the returned stream.

import { Readable } from 'node:stream';
import { createReadStream } from 'node:fs';

// With a synchronous mapper.
for await (const chunk of Readable.from([1, 2, 3, 4]).flatMap((x) => [x, x])) {
  console.log(chunk); // 1, 1, 2, 2, 3, 3, 4, 4
}
// With an asynchronous mapper, combine the contents of 4 files
const concatResult = Readable.from([
  './1.mjs',
  './2.mjs',
  './3.mjs',
  './4.mjs',
]).flatMap((fileName) => createReadStream(fileName));
for await (const result of concatResult) {
  // This will contain the contents (all chunks) of all 4 files
  console.log(result);
} 拷贝