SumOfUs/Champaign

.form-group.twitter-share
  = label_with_tooltip(form, :description, t('share.twitter.form.description'), t('tooltips.shares.link_explanation'))
  = form.text_area :description, class: 'form-control'
  p.char-count <span> x </span> of 280

javascript:
  $(function() {
    function getTweetLength(tweet) {
      tweet = tweet.replace('{LINK}', 'http://aurl.com');
      return Twitter.getTweetLength(tweet);
    }

    function updateForm(textarea) {
      var $textarea = $(textarea);
      var length = getTweetLength($textarea.val())
      if(length > 280) {
        // Twitter URLs use 23 chars. {LINK} length is 6
        // 280 - (23 - 6) = 263
        $textarea.val( $textarea.val().substr(0, 263) );
        length = 280;
      }
      $textarea.next('p.char-count').find('span').text(length);
    }

    $('.twitter-share textarea').on('change keyup paste', function(e) {
      updateForm(e.target);
    });

    $('.twitter-share textarea').each(function(i, textarea) {
      updateForm(textarea);
    });
  });