Vanilla (no jquery) fork; please comment or fork if you notice issues w/escaped html.

twitter-entities.js

/*
 * twitter-entities.js
 * This function converts a tweet with "entity" metadata 
 * from plain text to linkified HTML.
 *
 * See the documentation here: http://dev.twitter.com/pages/tweet_entities
 * Basically, add ?include_entities=true to your timeline call
 *
 * Based off existing code from Wade Simmons
 * Licensed under the MIT license
 * http://wades.im/mons
 *
 * Modified by lénaïc Terrier
 * Licensed under the MIT license
 * 
 * Vanilla JS fork by jack gold (@jackmakesthings)
 * Licensed under the MIT license
 */


function linkifyEntities(tweet)
{
	var frag = document.createElement('div');
	
	function escapeHTML(text) {
		frag.textContent = htmlCharsCorrect(text);
		return frag.innerHTML;
	}
  
  function htmlCharsCorrect(text)
  {
    text = text.replace(/&/g,'\u0026');
    text = text.replace(/>/g,'\u003E');
    text = text.replace(/</g,'\u003C');
    text = text.replace(/&(quot;|apos;)/g,'\u0022');
    text = text.replace(/'+/g,'\u0027');
    return text;
  }
  
  var
    index_map = {},
    result = "",
    last_i = 0,
    i = 0,
    end,
    func,
    emoji;
  
  var ranges = [
    '\ud83c[\udf00-\udfff]', // U+1F300 to U+1F3FF
    '\ud83d[\udc00-\ude4f]', // U+1F400 to U+1F64F
    '\ud83d[\ude80-\udeff]'  // U+1F680 to U+1F6FF
  ];
  var emojis = [];
  tweet.text = escapeHTML(tweet.text.replace(new RegExp(ranges.join('|'), 'g'), function(match, offset, string){
    emojis.push({
      offset: offset,
      char: match
    });
    return '\u0091';
  }));
  
  if (!(tweet.entities)) {
    return escapeHTML(tweet.text);
  }
  
	function processUrls(tweet) {
		if (!tweet.entities.urls) { return; }
		tweet.entities.urls.forEach(function(entry, index, entries) {
			index_map[entry.indices[0]] = [entry.indices[1], function(text) {
				return '<a href="' + entry.url + '" target="_blank">' + entry.display_url + '</a>';
			}]
		});
	};
	
	function processHashtags(tweet) {
		if (!tweet.entities.hashtags) { return; }
		tweet.entities.hashtags.forEach(function(entry, index, entries) {
			index_map[entry.indices[0]] = [entry.indices[1], function(text) {
				return '<a href="http://twitter.com/search/?q=#' + escapeHTML(entry.text) + '" target="_blank">' + text + '</a>';
			}]
		});
	}
	
	function processMentions(tweet) {
		
		if (!tweet.entities.user_mentions) { return; }
		tweet.entities.user_mentions.forEach(function(entry, index, entries) {
			index_map[entry.indices[0]] = [entry.indices[1], function(text) {
				return '<a href="http://twitter.com/' + escapeHTML(entry.screen_name) + '" target="_blank">' + text + '</a>';
			}]
		});	
	}
	
	processUrls(tweet);
	processHashtags(tweet);
	processMentions(tweet);

  for (i=0; i < tweet.text.length; ++i) {
    var ind = index_map[i];
    if (ind) {
      end = ind[0];
      func = ind[1];
      if (i > last_i) {
        result += escapeHTML(tweet.text.substring(last_i, i));
      }
      result += func(tweet.text.substring(i, end));
      i = end - 1;
      last_i = end;
    }
  }
  
  if (i > last_i) {
    result += escapeHTML(tweet.text.substring(last_i, i));
  }
  
  result = result.replace(/\u0091/g, function(match, offset, string){
    emoji = emojis.shift();
    return '<span class="emoji" data-emoji="u'+emoji.char.charCodeAt(0)+'">'+emoji.char+'</span>'
  });
  
  return result;
}