javascript 简单的Node.js转换流

Posted 2021-05-03

const fs = require('fs')
const { Transform } = require('stream')

const uppercaseChunk = (
  new Transform({
    transform(
      chunk,
      encoding,
      callback,
    ) {
      const stringifiedChunk = (
        chunk
        .toString()
      )

      this
      .push(
        stringifiedChunk
        .toUpperCase()
      )

      callback()
    },
  })
)

const readStream = (
  fs
  .createReadStream('./novel.txt')
)

const writeStream = (
  fs
  .createWriteStream('./uppercaseNovel.txt')
)

readStream
.pipe(uppercaseChunk)
.pipe(writeStream)

// uppercaseNovel.txt
// ... (lots of text) lorem ipsum
// ... (lots of uppercase text) LOREM IPSUM