Easily pickle/serialize/freeze/store and re-hydrate complex JavaScript objects (including Functions)


JSON on steroids.

Built for node.js and browsers. Cryo is inspired by Python's pickle and works similarly to JSON.stringify() and JSON.parse(). Cryo.stringify() and Cryo.parse() improve on JSON in these circumstances:

$ npm install cryo

Add the latest minified build to your project as a script:

<script type='text/javascript' src='cryo-0.0.4.js'></script>

Cryo has a very simple API that mimicks JSON:

  • Cryo.stringify(item)
  • Cryo.parse(string)
var Cryo = require('cryo');
var obj = {
  name: 'Hunter',
  created: new Date(),
  hellofunction() {
    console.log( + ' said hello in ' + this.created.getFullYear() + '!');
var frozen = Cryo.stringify(obj);
var hydrated = Cryo.parse(frozen);
hydrated.hello(); // Hunter said hello in 2013! 

Cryo takes a verbatim snapshot of all your properties, including those that are undefined - which JSON ignores.

var Cryo = require('../lib/cryo');
var obj = {
  defaultValue: undefined
var withJSON = JSON.parse(JSON.stringify(obj));
console.log(withJSON.hasOwnProperty('defaultValue'));   // false 
var withCryo = Cryo.parse(Cryo.stringify(obj));
console.log(withCryo.hasOwnProperty('defaultValue'));   // true 

Cryo successfully works with Date objects, which JSON.stringify() mangles into strings.

var Cryo = require('../lib/cryo');
var now = new Date();
var withJSON = JSON.parse(JSON.stringify(now));
console.log(withJSON instanceof Date);              // false 
var withCryo = Cryo.parse(Cryo.stringify(now));
console.log(withCryo instanceof Date);              // true 

JSON.stringify() makes multiple copies of single objects, losing object relationships. When several references to the same object are stringified with JSON, those references are turned into clones of each other. Cryo maintains object references so the restored objects are identical to the originals. This is easier to understand with an example:

var Cryo = require('../lib/cryo');
var userList = [{ name: 'Abe' }, { name: 'Bob' }, { name: 'Carl' }];
var state = {
  users: userList,
  activeUser: userList[1]
var withJSON = JSON.parse(JSON.stringify(state));
console.log(withJSON.activeUser === withJSON.users[1]);   // false 
var withCryo = Cryo.parse(Cryo.stringify(state));
console.log(withCryo.activeUser === withCryo.users[1]);   // true 

Cryo successfully stringifies and parses Infinity, which JSON mangles into null.

var Cryo = require('../lib/cryo');
var number = Infinity;
var withJSON = JSON.parse(JSON.stringify(number));
console.log(withJSON === Infinity);                 // false 
var withCryo = Cryo.parse(Cryo.stringify(number));
console.log(withCryo === Infinity);                 // true 

Objects, Arrays, Dates, and Functions can all hold properties, but JSON will only stringify properties on Objects. Cryo will recover properties from all containers:

var Cryo = require('../lib/cryo');
function first() {}
first.second = new Date();
first.second.third = [1, 2, 3];
first.second.third.fourth = { name: 'Hunter' };
try {
  var withJSON = JSON.parse(JSON.stringify(first));
  console.log( === 'Hunter');
} catch(e) {
  console.log('error');                                       // error 
var withCryo = Cryo.parse(Cryo.stringify(first));
console.log( === 'Hunter');  // true 

Cryo will stringify functions, which JSON ignores.

Note: Usually, if you've come up with a solution that needs to serialize functions, a better solution exists that doesn't. However, sometimes this can be enormously useful. Cryo will make faithful hydrated functions and objects with properties that are functions.

var Cryo = require('../lib/cryo');
function fn() {
  console.log('Hello, world!');
try {
  var withJSON = JSON.parse(JSON.stringify(fn));
} catch(e) {
  console.log('error');                             // error 
var withCryo = Cryo.parse(Cryo.stringify(fn));
withCryo();                                         // Hello, world! 

Tests require node.js.

$ git clone git://
$ cd cryo
$ make setup
$ make test