Added support for emojis and html specials characters.

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
 * 
 * Requires jQuery
 */

function linkifyEntities(tweet)
{
  function escapeHTML(text)
  {
    return $('<div/>').text(htmlCharsCorrect(text)).html();
  }
  
  function htmlCharsCorrect(text)
  {
    text = text.replace(/&amp;/g,'\u0026');
    text = text.replace(/&gt;/g,'\u003E');
    text = text.replace(/&lt;/g,'\u003C');
    text = text.replace(/&(quot;|apos;)/g,'\u0022');
    text = text.replace(/&#039;+/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);
  }
  
  if (tweet.entities.urls) {
    $.each(tweet.entities.urls, function(i,entry) {
      index_map[entry.indices[0]] = [entry.indices[1], function(text) {return "<a href='"+escapeHTML(entry.url)+"'>"+escapeHTML(entry.display_url)+"</a>";}];
    });
  }
  
  if (tweet.entities.hashtags) {
    $.each(tweet.entities.hashtags, function(i,entry) {
      index_map[entry.indices[0]] = [entry.indices[1], function(text) {return "<a href='http://twitter.com/search?q="+escape("#"+entry.text)+"'>"+escapeHTML(text)+"</a>";}];
    });
  }
  
  if (tweet.entities.user_mentions) {
    $.each(tweet.entities.user_mentions, function(i,entry) {
      index_map[entry.indices[0]] = [entry.indices[1], function(text) {return "<a title='"+escapeHTML(entry.name)+"' href='http://twitter.com/"+escapeHTML(entry.screen_name)+"'>"+escapeHTML(text)+"</a>";}];
    });
  }
  
  if(tweet.entities.hasOwnProperty('media')) {
    $.each(tweet.entities.media, function(i,entry) {
      index_map[entry.indices[0]] = [entry.indices[1], function(text) {return "<a class='mediahref' data-lightbox='"+entry.id+"' href='"+escapeHTML(entry.media_url)+"'></a>";}];
    });
  }
  
  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;
}

I don't recall anything about that piece of program. It was so long ago lol. Even the link to the twitter documentation is dead now... I guess emojis may have been messing with the length of the text because emojis are two characters when the text is utf-8 encoded. Sorry I couldn't be of more help.