Pure Javascript - store object in cookie

Question

No jQuery.

I want to store an object or array in a cookie.

The object should be usable after page refresh.

How do I do that with pure JavaScript? I read many posts, but do not know how to serialize appropriately.

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EDIT: Code:

var instances = {}; ... instances[strInstanceId] = { container: oContainer }; ... instances[strInstanceId].plugin = oPlugin; ... JSON.stringify(instances);  // throws error 'TypeError: Converting circular structure to JSON' 

1. How do I serialize instances?

2. How do I maintain functionality, but change structure of instance to be able to serialize with stringify?

Answer 1

Try that one to write

function bake_cookie(name, value) {   var cookie = [name, '=', JSON.stringify(value), '; domain=.', window.location.host.toString(), '; path=/;'].join('');   document.cookie = cookie; } 

To read it take:

function read_cookie(name) {  var result = document.cookie.match(new RegExp(name + '=([^;]+)'));  result && (result = JSON.parse(result[1]));  return result; } 

To delete it take:

function delete_cookie(name) {   document.cookie = [name, '=; expires=Thu, 01-Jan-1970 00:00:01 GMT; path=/; domain=.', window.location.host.toString()].join(''); } 

To serialize complex objects / instances, why not write a data dump function in your instance:

function userConstructor(name, street, city) {    // ... your code    this.dumpData = function() {      return {         'userConstructorUser': {             name: this.name,             street: this.street,             city: this.city          }        }     } 

Then you dump the data, stringify it, write it to the cookie, and next time you want to use it just go:

  var mydata = JSON.parse(read_cookie('myinstances'));   new userConstructor(mydata.name, mydata.street, mydata.city); 

Answer 2

Use either object's own .toString() method if it gives meaningful serialization or JSON.stringify(). Do note, however, that cookies are usually limited in length and won't be able to hold big amounts of data.