Replace URLs with links and unicode emoji with images.

handlebars-formatTextForHTML.coffee

LINK_DETECTION_REGEX = /(([a-z]+:\/\/)?(([a-z0-9\-]+\.)+([a-z]{2}|aero|arpa|biz|com|coop|edu|gov|info|int|jobs|mil|museum|name|nato|net|org|pro|travel|local|internal))(:[0-9]{1,5})?(\/[a-z0-9_\-\.~]+)*(\/([a-z0-9_\-\.]*)(\?[a-z0-9+_\-\.%=&]*)?)?(#[a-zA-Z0-9!$&'()*+.=-_~:@/?]*)?)(\s+|$)/gi

EMOJI_DIRECTORY = "/path/to/assets/emoji/20x20"

# Handlebars is presumed, but you could swap out 
ESCAPE_EXPRESSION_FUNCTION = Handlebars.Utils.escapeExpression
MARKSAFE_FUNCTION = (str) -> new Handlebars.SafeString(str) 


# Emoji unicode chars become images.
emojify = (safeContent) ->
  safeContent.replace /([\ue001-\ue537])/g, (emoji) ->
    filename = emoji.charCodeAt(0).toString(16).toUpperCase()
    "<img class='emoji' src='#{EMOJI_DIRECTORY}/#{filename}.png'/>"   # TODO: alt and title

# Replace URLs like https://github.com with <a href='https://github.com'>github.com</a>
linkify = (safeContent) ->
  safeContent.replace LINK_DETECTION_REGEX, (url) ->
      address = if /[a-z]+:\/\//.test url then url else "http://#{url}"
      url = url.replace /^https?:\/\//, ''
      "<a href='#{address}' target='_blank'>#{url}</a>"

# Helper for formatting strings with links and line breaks for display in HTML
formatTextForHTML = (content) ->
  # Start by escaping expressions in the content to make them safe.
  safeContent = ESCAPE_EXPRESSION_FUNCTION(content)
  safeContent = linkify safeContent
  # Line breaks become <br/>'s
  safeContent = safeContent.replace /\n/g, '<br/>'
  safeContent = emojify safeContent
  MARKSAFE_FUNCTION(safeContent) # Mark our string as safe, since it is.
  
Handlebars.registerHelper 'formatTextForHTML', formatTextForHTML

The regex really is almost perfect. One issue is if you end a sentence with a link, then it does not detect, like, "For more information check out our site at www.mysite.com. There you can find anything your heart desires!"