compose-streams.js

//normally to pipe a -> b -> c:
a.pipe(b).pipe(c)

//could also compose pipings, this below is the same as above, (or is it?):
a.pipe(b.pipe(c))

//makes more sense when using a variable to define a composed piping instance
const bc = b.pipe(c)
a.pipe(bc)
d.pipe(bc)

split-stream.js

const through = require('through');

const a = through(function write(chunk) {this.push({data:`you said ${chunk}`})})
const b = through(function write(chunk) {chunk.data+='...at ';this.push(chunk)})
const c = through(function write(chunk) {chunk.data+=(new Date)+'\n';this.push(chunk)})

const d = through(function write(chunk) {this.push(chunk.data)})

const astream = process.stdin.pipe(a)

//splitting the transform and output to different streams
astream.pipe(b).pipe(c)
astream.pipe(d).pipe(process.stdout)

// $ echo hi | node streamy.js
// => you said hi
// => ...at Sun Jul 09 2017 00:47:34 GMT-0400 (EDT)


//order matters here
astream.pipe(d).pipe(process.stdout)
astream.pipe(b).pipe(c)

// $ echo hi | node streamy.js
// => hi