Override markdown button to support code blocks

gistfile1.js

  //$.fn.markdown.defaults.buttons[0][2].data[2]
  var cmdBold, cmdItalic, cmdCode;
  $.fn.markdown.defaults.buttons[0].forEach(function(group) {
    group.data.forEach(function(button) {
      if (button.name === 'cmdBold') cmdBold = button;
      else if (button.name === 'cmdItalic') cmdItalic = button;
      else if (button.name === 'cmdCode') cmdCode = button;
    });
  });
  // Override `cmdCode` button;
  if (cmdCode) {
    cmdCode.callback = function(e) {
      var cursor,
          selected = e.getSelection(),
          content = e.getContent(),
          chunk = selected.length === 0 ? e.__localize('code text here') : selected.text;

      if (content.substr(selected.start - 4, 4) === '```\n'
        && content.substr(selected.end, 4) === '\n```') {
        e.setSelection(selected.start - 4, selected.end + 4);
        e.replaceSelection(chunk);
        cursor = selected.start - 4;
      } else if (content.substr(selected.start - 1, 1) === '`'
        && content.substr(selected.end, 1) === '`') {
        e.setSelection(selected.start - 1, selected.end + 1);
        e.replaceSelection(chunk);
        cursor = selected.start - 1;
      } else if (content.indexOf('\n') > -1) {
        e.replaceSelection('```\n' + chunk + '\n```');
        cursor = selected.start + 4;
      } else {
        e.replaceSelection('`' + chunk + '`');
        cursor = selected.start + 1;
      }

      e.setSelection(cursor, cursor + chunk.length);
    };
  }

  $('[data-provide="markdown"]').markdown({
    additionalButtons: [
      [
        {
          name: "groupFont2",
          data: [
            cmdBold
          ]
        }
      ]
    ],
    reorderButtonGroups: [
      'groupFont',
      'groupLink',
      'groupMisc',
      /*{
        'groupMisc': [
          'cmdList',
          'cmdListO',
          'cmdCodeMultiLine',
          'cmdQuote'
        ]
      },*/
      'groupUtil'
    ]
  });

Related:
OpenUserJS/OpenUserJS.org#402
refactory-id/bootstrap-markdown#136