Use of reduce for word counting

README.md

Reduce a list of words to counts for each unique word.

index.coffee

{deepEqual} = require 'assert'

counts = (words) ->
  toCounts = (totals, word) ->
    totals[word] ?= 0  # initialize if not yet totalsed
    totals[word] += 1  # increment otherwise
    totals
  words.reduce toCounts, totals={}

words = ['a', 'a', 'b']   # words to count

expected =                # expected result
  a: 2
  b: 1

deepEqual counts(words), expected

nonreduce-version.coffee

{deepEqual} = require 'assert'

counts = (words) ->
  totals = {}
  totals[w] = (totals[w] or 0) + 1 for w in words
  totals

deepEqual counts(['a', 'a', 'b']),
  a: 2
  b: 1