wordcount.js

;(function(window, document, undefined) {
  'use strict';

  // ensure only one instance is running at a time
  if (window._fz_wordcloud) return;
  window._fz_wordcloud = true;

  var MAX_WORDS      = 50;
  var BASE_FONT_SIZE = 12;

  var words = document.body.innerText.toLowerCase()
    .replace(/[\.,-\/#!$%\^&\*;:{}=\-_`~()?]/g, '').split(/[\s\/]+/g).sort();

  var counts = {};
  var result = [];

  words.forEach(function(val) {
    if (val.length < 4) return;
    counts[val] = counts[val] ? counts[val] + 1 : 1;
  });

  for (var word in counts) {
    result.push({ word: word, count: counts[word] });
  }

  function sortBy(array, property) {
    return array.sort(function(a, b) {
      if (a[property] < b[property]) return -1;
      if (a[property] > b[property]) return 1;
      return 0; // a[property] === b[property]
    });
  }

  // sort by count, return most used words, then sort alphabetically
  result = sortBy(sortBy(result, 'count').slice(-MAX_WORDS), 'word');

  var container = document.createElement('div');
  var p         = document.createElement('p');

  container.style.background = '#fff';
  container.style.position   = 'fixed';
  container.style.top        = 0;
  container.style.right      = 0;
  container.style.width      = '100%';
  container.style.height     = '100%';
  container.style.zIndex     = Number.MAX_SAFE_INTEGER || 9007199254740991;

  p.style.fontColor = '#ccc';
  p.style.padding   = '50px';
  p.style.width     = '50%';
  p.style.textAlign = 'justify';
  p.style.margin    = '0 auto';

  container.appendChild(p);
  
  // display in div with font-size according to frequency
  result.forEach(function(obj) {
    var space = document.createTextNode(' ');
    var span  = document.createElement('span');

    span.innerText      = obj.word;
    span.style.fontSize = BASE_FONT_SIZE + obj.count + 'px';

    p.appendChild(space);
    p.appendChild(span);
  });

  document.body.appendChild(container);

  // destroy the container on click
  container.addEventListener('click', function(e) {
    document.body.removeChild(container);
    container.removeEventListener('click');

    window._fz_wordcloud = undefined;
  });
})(window, document);