Skip to content

Instantly share code, notes, and snippets.

@joyrexus

joyrexus/README.md

Created February 18, 2014 16:30
Show Gist options
  • Star 0 You must be signed in to star a gist
  • Fork 0 You must be signed in to fork a gist
  • Save joyrexus/9074340 to your computer and use it in GitHub Desktop.
Save joyrexus/9074340 to your computer and use it in GitHub Desktop.
Download ZIP
Object stream reducer demo
Raw
README.md

Demonstrate how to extend stream's Transform base class to create reducers for streamed objects.

count = new Counter
iter = (memo, d) -> memo + d
sum = new Reduce(iter, 0)
 
count
  .upto(5)
  .pipe(sum)  # 1 + 2 + 3 + 4 = 10
Raw
index.coffee
###
Demonstrate how to extend stream's Transform base class
to create reducers for streamed objects.
iter = (memo, d) -> memo + d
sum = new Reduce(iter, 0)
count
.upto(5)
.pipe(sum) # 1 + 2 + 3 + 4 = 10
###
Read = require('stream').Readable
Transform = require('stream').Transform
class Counter extends Read
constructor: (@max) ->
@i = 0
super(objectMode: true)
upto: (n) ->
@max = n
@
_read: ->
@i += 1
if @max and @i >= @max
@push null
else
@push @i
class Reduce extends Transform
constructor: (@reduce, @memo) ->
super(objectMode: true)
_transform: (data, enc, next) ->
@memo = @reduce(@memo, data)
next()
_flush: (done) ->
process.stdout.write @memo + "\n"
done()
count = new Counter
iter = (memo, d) -> memo + d
sum = new Reduce(iter, 0)
count
.upto(5)
.pipe(sum) # 1 + 2 + 3 + 4 = 10
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment