showdown/src/subParsers/strikethrough.js

showdown.subParser('strikethrough', function (text, options, globals) {
  'use strict';

  function parseInside (txt) {
    if (options.simplifiedAutoLink) {
      txt = showdown.subParser('simplifiedAutoLinks')(txt, options, globals);
    }
    return '<del>' + txt + '</del>';
  }

  if (options.strikethrough) {
    text = globals.converter._dispatch('strikethrough.before', text, options, globals);
    text = text.replace(/(?:~){2}([\s\S]+?)(?:~){2}/g, function (wm, txt) { return parseInside(txt); });
    text = globals.converter._dispatch('strikethrough.after', text, options, globals);
  }

  return text;
});