const composeCPS = (f, g) => {
  return (x, cb) => {
    g(x, y => {
      f(y, z => {
        cb(z)
      })
    })
  }
}

// Then it can compose again
const readFileContentCPS = composeCPS(readFileCPS, readFileCPS)
readFileContentCPS('./file1', result => console.log(result))