showdown-footnotes.js

(function () {
  var footnotes = function () {
    return [
      { type: 'lang', filter: function(text) {
        // Use footnotes like so: "foo[^1](This is the footnote text)"
        var i = 0;
        var inline_regex = /\[\^(\d|n)\]\((.*?)\)/g;
        text = text.replace(inline_regex, function(match, n, t) {
          // We allow both automatic and manual footnote numbering
          if (n == "n") n = i+1;

          var s = '<span class="footnote">' +
                    '<sup class="footnote__counter" tabindex="0">'+n+'</sup>' +
                    '<span class="footnote__text bg-color-secondary"><sup class="footnote__text__counter">'+n+'</sup>'+t+'</span>' +
                  '</span>';
          i += 1;
          return s;
        });

        return text;
      }}
    ];
  };

  // Client-side export
  if (typeof window !== 'undefined' && window.Showdown && window.Showdown.extensions) {
    window.Showdown.extensions.footnotes = footnotes;
  }

}());