This is an AngularJS filter to linkify #hashtags and @mention texts into respective Twitter URLsDemo - http://plnkr.co/edit/vrdgxU?p=preview

hashtagLinky.js

/* Based on https://gist.github.com/rishabhmhjn/7028079 */
function HashtagLinky($filter, $sce) {
  'ngInject'

    return function(text, target) {
      if (!text) return text;

      var replacedText = $filter('linky')(text, target);
      var targetAttr = "";
      if (angular.isDefined(target)) {
          targetAttr = ' target="' + target + '"';
      }

      // replace #hashtags
      var replacePattern1 = /(^|\s)#(\w*[a-zA-Z_]+\w*)/gim;
      replacedText = replacedText.replace(replacePattern1, '$1<a href="https://twitter.com/search?q=%23$2"' + targetAttr + '>#$2</a>');

      $sce.trustAsHtml(replacedText);
      return replacedText;
    };
}

export default HashtagLinky;

This is the modern Angular 1.5 version of this filter