async stream

index.js

var count = 0

function asyncFn (cb) {
  setTimeout(function () {
    console.log('emit new chunk')
    return cb(null, {foo: 'bar'})
  }, 500)
}

module.exports = function () {
  return from(function (size, next) {
    if (count < 5) {
      ++count
      asyncFn(function (err, chunk) {
        next(null, chunk)
      })
    } else {
      next(null, null)
    }
  })
}

log

emit new chunk
{ foo: 'bar' }
✖ undefined: stream.push() after EOF

now better using if else instead of while and return