sequentialCallback.js

function sequentialCallback (...fns) {
  return (...args) => {
    const done = args.pop()
    const next = (error, ...args) => {
      if (error) return done(error)
      if (fns.length) {
        const fn = fns.shift()
        return fn(...args, next)
      }
      return done(null, ...args)
    }
    return next(null, ...args)
  }
}