replaceContent.js

const fs = require('fs')
const cwd = process.cwd()

const contentToDelete = `    <link rel="SHORTCUT ICON" href="https://37signals.com/images/37.ico" />`

const file = 'ch01_About_37signals - Copy.html'

const replaceContent = (file, from, to) => {
  fs.readFile(file, 'utf8', (err, data) => {
    if (err)
      throw err

    const newContent = data.split(from).join(to)
    fs.writeFile(file, newContent, (err) => {
      if (err)
        throw err
      
      console.log(data)
    })
  })
}

fs.readdir(cwd, 'utf8', (err, files) => {
  if (err)
    throw err

  files
    .filter(f => f.endsWith('.html'))
    .map(f => replaceContent(f, contentToDelete, ''))
})