Javascript 如何在不将整个文件加载到内存的情况下，在Node.js中实现Unix粘贴命令

import { open as fsOpenAsync } from 'node:fs/promises'
import { createWriteStream } from 'node:fs'

const filenames = ['a.txt', 'b.txt', 'c.txt']
const outname = 'out.txt'

await paste(filenames, outname)

/**
 * Read multiple files line by line and write lines concatenated by `\t`
 */
async function paste(from: string[], to: string) {
  const files = await Promise.all(filenames.map(fn => fsOpenAsync(fn)))
  const zip = zipAsyncs(files.map(f => f.readLines()[Symbol.asyncIterator]()))
  const writeStream = createWriteStream(to, { flags: 'w' })
  for await (const lines of zip)
    writeStream.write(`${lines.map(e => e ?? '').join('\t')}\n`)
  writeStream.close()
  await Promise.all(files.map(f => f.close()))
}

/**
 * Zip multiple async iterables, returning `undefined` for missing values
 * @template {T}
 * @param {AsyncIterator<T>[]} its
 * @returns {AsyncGenerator<IteratorResult<T | undefined, any>[]>}
 */
async function* zipAsyncs(its) {
  while (true) {
    const results = await Promise.all(its.map(e => e.next()))
    yield results.map(r => r.value)
    if (results.every(r => r.done))
      return
  }
}