anchor-extension.js

(function (extension) {
  'use strict';

  if (typeof showdown !== 'undefined') {
    // global (browser or nodejs global)
    extension(showdown);
  } else if (typeof define === 'function' && define.amd) {
    // AMD
    define(['showdown'], extension);
  } else if (typeof exports === 'object') {
    // Node, CommonJS-like
    module.exports = extension(require('showdown'));
  } else {
    // showdown was not found so we throw
    throw Error('Could not find showdown library');
  }

}(function (showdown) {
  'use strict';

  /**
   * 支持 <h1> 到 <h6> 标题的锚点按钮
   * 
   * Support for anchor buttons for <h1> to <h6> titles
   */
  showdown.extension('anchor', function () {
    return [

      {
        type:    'output',
        regex:   '<h\\d id="(.+?)">(.*?)<\\/h(\\d)>',
        replace: function (match, id, title, level) {

          // github anchor style
          var octicon_html = `<a class="anchor" aria-hidden="true" href="#${id}"><svg class="octicon" viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>`;

          return `<h${level} id="${id}">${octicon_html}${title}</h${level}>`;
        }
      },

    ];
    
  });

}));