gistfile1.js

let self = require('self'), file = require('file'), url = require('url');
let contextMenu = require('context-menu');
let sym = gensym(), containerID = 'word-cloud-' + sym;

let item = contextMenu.Item({
  label: "Show Word Cloud",
  onClick: function(context, item) {
    let win = context.window, corpus = generateCorpus(win);
    let scores = score(corpus), sorted = plist(scores);
    sorted.sort(byScore);

    let scripts = ['jquery-1.4.2.js', 'jquery.masonry.js'];
    if (!win.wrappedJSObject[sym]) {
      loadScripts(win, scripts.map(self.data.url), function(win) {
        setup(win, corpus, sorted);
      });
    } else {
      arrange(win.wrappedJSObject[sym].jQuery, win, corpus, sorted);
    }
  },
  context: function(context) {
    return context.window.location != 'about:blank' &&
           !context.document.getElementById(containerID);
  }
});
contextMenu.add(item);

function loadScripts(win, scripts, callback) {
  let length = scripts.length, loaded = 0, w = win.wrappedJSObject;
  let head = w.document.getElementsByTagName('head')[0];

  for (let i = 0; i < length; i++) {
    let s = w.document.createElement('script');
    s.addEventListener('load', function incr() {
      loaded++;
      if (loaded == length) callback(win);
    }, false);
    s.src = scripts[i];
    head.appendChild(s);
  }
}

function setup(win, corpus, sorted) {
  let doc = win.document;
  let $ = (function(win) {
    win[sym] = {};
    return (win[sym].jQuery = win.jQuery.noConflict(true));
  })(win.wrappedJSObject);

  $.fn.rotate = function rotate(deg) {
    if (deg != 90 && deg != 270) throw new Error();
    return this.each(function() {
      let e = $(this.wrappedJSObject || this);
      e.css({display: 'inline', cursor: 'vertical-text'});
      let w = e.width(), h = e.height();
      e.css({display: 'inline-block', MozTransformOrigin: 'left top'});

      let style = {height: w + 'px', width: h + 'px'};
      let t = ['rotate(' + deg + 'deg) translate', null, 'px)'];
      t[1] = (deg == 90) ? 'Y(-' + h : 'X(-' + w;
      style.MozTransform = t.join('');
      e.css(style);
    });
  };

  arrange($, win, corpus, sorted);
}

Math.randomIntBetween = function randomIntBetween(min, max) {
  // jsocol's overkill randomInt
  return Math.floor((Math.random()-0.5)*(max - min) + min + (max - min)/2);
};

let colors = [
  '#b00', '#aff849', '#ff8000', '#ff0080', '#b0b', '#0080ff', '#ccc'
];
colors.randomItem = function randomItem() {
  return this[Math.randomIntBetween(0, this.length - 1)];
};

function arrange($, win, corpus, sorted) {
  let doc = win.wrappedJSObject.document;
  let container = $('<div>', doc).css({
    display: 'block', position: 'absolute',
    top: 0, left: 0, right: 0, bottom: 0,
    overflowX: 'hidden', overflowY: 'scroll', backgroundColor: 'black'
  }).attr('id', containerID);

  let close = $('<a>', doc).html('Close').attr('title', 'Close').css({
    display: 'block', position: 'fixed', overflow: 'hidden', zIndex: 1,
    width: '42px', height: 0, paddingTop: '42px', cursor: 'pointer',
    backgroundImage: 'url(' + self.data.url('close-button.png') + ')'
  }).click(function() {
    $(doc.body).show();
    container.remove();
  });
  container.append(close);

  let stage = $('<div>', doc).css({
    padding: '3em', width: '100%', height: '100%', zIndex: 0
  });
  container.append(stage);

  $(doc.body.parentNode).append(container);

  let parts = [[], []];
  for (let i = 0, length = sorted.length; i < length; i++)
    parts[i % 2].push(sorted[i]);
  parts[0].reverse();

  let weighted = parts[0].concat(parts[1]);
  let bodyFont = $(doc.body).css('fontFamily');
  weighted.forEach(function([word, score]) {
    let e = $('<div>', doc).html(word).css({
      display: 'inline-block', fontFamily: bodyFont,
      color: colors.randomItem(), fontSize: (score * 1.5) + 'em'
    }).addClass('word').hide();
    stage.append(e);

    let n = Math.randomIntBetween(0, 8);
    (n == 1 || n == 3) && e.rotate(90);
    (n == 2 || n == 4) && e.rotate(270);
    e.show();
  });

  stage.masonry({itemSelector: '.word', resizeable: false});
  $(doc.body).hide();
}

let expr = [
  '//text()[normalize-space(.)]',
  '[name(..)!="SCRIPT"][name(..)!="script"]',
  '[name(..)!="STYLE"][name(..)!="style"]',
  '[name(..)!="TEXTAREA"][name(..)!="textarea"]',
  '[name(..)!="NOSCRIPT"][name(..)!="noscript"]'
].join('');

function generateCorpus(win) {
  let results = [], query = win.document.evaluate(
    expr, win.document, null,
    win.wrappedJSObject.XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null
  );
  for (let i = 0, length = query.snapshotLength; i < length; i++)
    results.push(query.snapshotItem(i).textContent);
  return results.join(' ');
}

let commonEnglishWords = [
  'the', 'be', 'to', 'of', 'and', 'a', 'in', 'that', 'have', 'I', 'it',
  'for', 'not', 'on', 'with', 'he', 'as', 'you', 'do', 'at', 'this',
  'but', 'his', 'by', 'from', 'they', 'we', 'say', 'her', 'she', 'or',
  'an', 'will', 'my', 'one', 'all', 'would', 'there', 'their', 'what',
  'so', 'up', 'out', 'if', 'about', 'who', 'get', 'which', 'go', 'me',
  'when', 'make', 'can', 'like', 'time', 'no', 'just', 'him', 'know',
  'take', 'people', 'into', 'year', 'your', 'good', 'some', 'could',
  'them', 'see', 'other', 'than', 'then', 'now', 'look', 'only', 'come',
  'its', 'over', 'think', 'also', 'back', 'after', 'use', 'two', 'how',
  'our', 'work', 'first', 'well', 'way', 'even', 'new', 'want', 'because',
  'any', 'these', 'give', 'day', 'most', 'us', 'is', 'are'
];

function score(corpus) {
  let words = {};
  corpus.replace(/[A-Za-z_ ]+?(\s|$)/g, function(w) {
    w = w.toLowerCase().trim();
    if (w.length <= 3) return;
    if (!words[w]) words[w] = 0;
    words[w]++;
  });
  return words;
}

function plist(object) [[key, object[key]] for (key in object)];
function gensym() Math.round(Math.random() * 1e16).toString(36);
function byScore(a, b) b[1] - a[1];