simple-concat 
Super-minimalist version of concat-stream. Less than 15 lines!
install
npm install simple-concat
usage
This example is longer than the implementation.
var s = new stream.PassThrough()
concat(s, function (err, buf) {
if (err) throw err
console.error(buf)
})
s.write('abc')
setTimeout(function () {
s.write('123')
}, 10)
setTimeout(function () {
s.write('456')
}, 20)
setTimeout(function () {
s.end('789')
}, 30)license
MIT. Copyright (c) Feross Aboukhadijeh.