Sergo File Watcher

sergo.js

const path = require("path")
const fs = require("fs")
const endOfLine = require("os").EOL

// Config -
const fileDir = __dirname
const fileName = "in-file.txt"

const outFileDir = __dirname
const outFileName = "out-file.txt"
// - Config

const filePath = path.resolve(fileDir, fileName)
const outFilePath = path.resolve(outFileDir, outFileName)

fs.watchFile(
  filePath,
  { interval: 1000 /* time in millisecond */ },
  ({ mtime: currentModifiedTime }, { mtime: previousModifiedTime }) => {
    if (currentModifiedTime !== previousModifiedTime) {
      const fileContent = fs.readFileSync(filePath)
      const outFileExists = fs.existsSync(outFilePath)

      fs.appendFileSync(
        outFilePath,
        outFileExists ? endOfLine + fileContent : fileContent
      )
    }
  }
)