this shows how to implement a ruby feature ( http://conv.denshochan.com/markdown#ruby ). tested on node 0.10.30 & markdown-js 0.5.0

markdown-js-dialect-example.js

var Markdown = require('markdown').markdown.Markdown;
var MyDialect = Markdown.subclassDialect(Markdown.dialects.Gruber);
MyDialect.inline['{'] = function inline_ruby(text, matches, out) {
    var m = text.match(/^\{(.+)\|(.+)\}/);
    if (m) {
        return [m[0].length, ['ruby', m[2], m[1]]];
    } else {
        // no match
        return [1, '{'];
    }
};
Markdown.buildBlockOrder(MyDialect.block);
Markdown.buildInlinePatterns(MyDialect.inline);
var parser = new Markdown(MyDialect);
console.log(parser.toTree('{hello|world}'));