ghost/core/server/utils/markdown-converter.js

var MarkdownIt  = require('markdown-it'),
    converter = new MarkdownIt({
        html: true,
        breaks: true,
        linkify: true
    })
    .use(require('markdown-it-footnote'))
    .use(require('markdown-it-lazy-headers'))
    .use(require('markdown-it-mark'))
    .use(function namedHeaders(md) {
        // jscs:disable

        // match legacy Showdown IDs
        var slugify = function (inputString, usedHeaders) {
            var slug = inputString.replace(/[^\w]/g, '').toLowerCase();
            if (usedHeaders[slug]) {
                usedHeaders[slug] += 1;
                slug += usedHeaders[slug];
            }
            return slug;
        };
        var originalHeadingOpen = md.renderer.rules.heading_open;

        // originally from https://github.com/leff/markdown-it-named-headers
        // moved here to avoid pulling in http://stringjs.com dependency
        md.renderer.rules.heading_open = function (tokens, idx, something, somethingelse, self) {
            var used_headers = {};

            tokens[idx].attrs = tokens[idx].attrs || [];

            var title = tokens[idx + 1].children.reduce(function (acc, t) {
                return acc + t.content;
            }, '');

            var slug = slugify(title, used_headers);
            tokens[idx].attrs.push(['id', slug]);

            if (originalHeadingOpen) {
                return originalHeadingOpen.apply(this, arguments);
            } else {
                return self.renderToken.apply(self, arguments);
            }
        };
        // jscs:enable
    });

module.exports = {
    render: function (markdown) {
        return converter.render(markdown);
    }
};