Count words of each length in a string of text

word-count.js

var pluralise = function(count, single, plural) {
  return String(count) + ' ' + (count === 1 ? single : plural);
}

// zero-fill an array of 20 items
var input = Array.apply(null, new Array(20)).map(Number.prototype.valueOf, 0);

// match words
p.match(/\b(\w+)\b/g).map(function(word) { 
  // get the length of each word
  return word.length; 
}).reduce(function(counts, letters) { 
  // increment the counter for the word length
  counts[letters]++;
  return counts;
}, input).map(function(count, letters) { 
  // generate text
  return pluralise(count, 'word', 'words') + ' with ' + pluralise(letters, 'letter', 'letters') 
}).join('\n')