Jekyll - Parse YAML frontmatter in a string

frontmatter.rb

module Jekyll
  module YamlParser

    def yamlparser(string = '', options = {})
      options = {delimiter: '---', parser: YAML, remove: nil}.merge(options)

      # convert string params to symbols
      options = options.inject({}) {|memo, (k,v)| memo[k.to_sym] = v; memo}

      @delimiter = options[:delimiter]
      @parser = options[:parser]
      @remove = options[:remove]

      # if you have extra stuffs in front of your YAML, like ```
      unless @remove.nil?
        string.tr!(@remove, '')
      end

      res = [{},'']
      res[1] = string.lstrip.gsub(/#{@delimiter}(.*)#{@delimiter}/m) do |match|
        res[0] = @parser.load($~.captures.first.strip)
        ''
      end.strip
      res
    end
  end
end

Liquid::Template.register_filter(Jekyll::YamlParser)