Handle cookies betwen JavaScript and Rails with JSON/Hash objects

application.js

window.cookies = {
  set: function(name, value, days) {
    if (name) {
      if (days) {
        var date = new Date();
        date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
        var expires = "; expires=" + date.toGMTString();
      }
      else {
        var expires = "";
      }
      document.cookie = name + "=" + escape(value) + expires + "; path=/";
    }
  },
  
  setJSON: function(name, value, days) {
    this.set(name, Object.toJSON(value), days); // toJSON() requires Prototype.js
  },
  
  get: function(name) {
    if (name) {
      var match = document.cookie.match(new RegExp(name + "=(.*?)(?:;|$)"));      
      if (match) {
        return unescape(match[1].replace(/\+/g, "%20"));
      }
    }
  },
  
  getJSON: function(name) {
    var value = this.get(name);
    if (value) {
      return value.evalJSON(); // evalJSON() requires Prototype.js
    }
  },
  
  list: function() {
    var matches = document.cookie.split(new RegExp("=|; "));
    if (matches.length > 1) {
      var cookies = new Array(matches.length / 2);
      for (var i = j = 0; j < matches.length; j+=2) {
        cookies[i++] = matches[j]
      }
      return cookies;
    }
  },
  
  delete_: function(name) {
    this.set(name, "" , -1);
  }
}

application.rb

before_filter :json_cookies

protected
  
def json_cookies
  request.cookies.each do |key, value|
    request.cookies[key] = ActiveSupport::JSON.decode(request.cookies[key])
  end
end

example.js

// client side
// using prototype.js

cookies.setJSON('data', [{"name": "alice", "job": "programmer"}, {"name": "bob", "job": "administrator"}]);

cookies.getJSON('data')               // [Object name=alice job=programmer, Object name=bob job=administrator]
cookies.getJSON('data').first()       // Object name=alice job=programmer
cookies.getJSON('data').first().name; // "alice"

example.rb

# server side

cookies["data"]               # => [{"name" => "alice", "job" => "programmer"}, {"name" => "bob", "job" => "administrator"}]
cookies["data"].first         # => {"name" => "alice", "job" => "programmer"}
cookies["data"].first["name"] # => "alice"