showdownjs/src/subParsers/makemarkdown/listItem.js

showdown.subParser('makeMarkdown.listItem', function (node, globals) {
  'use strict';

  var listItemTxt = '';

  var children = node.childNodes,
      childrenLenght = children.length;

  for (var i = 0; i < childrenLenght; ++i) {
    listItemTxt += showdown.subParser('makeMarkdown.node')(children[i], globals);
  }
  // if it's only one liner, we need to add a newline at the end
  if (!/\n$/.test(listItemTxt)) {
    listItemTxt += '\n';
  } else {
    // it's multiparagraph, so we need to indent
    listItemTxt = listItemTxt
      .split('\n')
      .join('\n    ')
      .replace(/^ {4}$/gm, '')
      .replace(/\n\n+/g, '\n\n');
  }

  return listItemTxt;
});