Save Javascript objects in sessionStorage

问题:

SessionStorage and LocalStorage allows to save key/value pairs in a web browser. The value must be a string, and save js objects is not trivial.

var user = {'name':'John'};
sessionStorage.setItem('user', user);
var obj = sessionStorage.user; // obj='[object Object]' Not an object

Nowadays, you can avoid this limitation by serializing objects to JSON, and then deserializing them to recover the objects. But the Storage API always pass through the setItem and getItem methods.

sessionStorage.setItem('user', JSON.stringify(user));
var obj = JSON.parse(sessionStorage.getItem('user')); // An object :D

Can I avoid this limitation?

I just want to execute something like this:

sessionStorage.user.name; // 'John'
sessionStorage.user.name = 'Mary';
sessionStorage.user.name // 'Mary'

I have tried the defineGetter and defineSetter methods to intercept the calls but its a tedious job, because I have to define all properties and my target is not to know the future properties.

回答1:

Either you can use the accessors provided by the Web Storage API or you could write a wrapper/adapter. From your stated issue with defineGetter/defineSetter is sounds like writing a wrapper/adapter is too much work for you.

I honestly don't know what to tell you. Maybe you could reevaluate your opinion of what is a "ridiculous limitation". The Web Storage API is just what it's supposed to be, a key/value store.

回答2:

Could you not 'stringify' your object...then use sessionStorage.setItem() to store that string representation of your object...then when you need it sessionStorage.getItem() and then use $.parseJSON() to get it back out?

Working example http://jsfiddle.net/pKXMa/

回答3:

The solution is to stringify the object before calling setItem on the sessionStorage.

var user = {'name':'John'};
sessionStorage.setItem('user', JSON.stringify(user));
var obj = JSON.parse(sessionStorage.user);

回答4:

This is a dynamic solution which works with all value types including objects :

class Session extends Map {
  set(id, value) {
    if (typeof value === 'object') value = JSON.stringify(value);
    sessionStorage.setItem(id, value);
  }

  get(id) {
    const value = sessionStorage.getItem(id);
    try {
      return JSON.parse(value);
    } catch (e) {
      return value;
    }
  }
}

Then :

const session = new Session();

session.set('name', {first: 'Ahmed', last : 'Toumi'});
session.get('name');

回答5:

Use case:

 sesssionStorage.setObj(1,{date:Date.now(),action:'save firstObject'});
 sesssionStorage.setObj(2,{date:Date.now(),action:'save 2nd object'}); 
 //Query first object
  sesssionStorage.getObj(1)
  //Retrieve date created of 2nd object
  new Date(sesssionStorage.getObj(1).date)

API

Storage.prototype.setObj = function(key, obj) {

        return this.setItem(key, JSON.stringify(obj))
    };

    Storage.prototype.getObj = function(key) {
        return JSON.parse(this.getItem(key))
    };

回答6:

    var user = {'name':'John'};
    sessionStorage['user'] = JSON.stringify(user);
    console.log(sessionStorage['user']);

回答7:

You could also use the store library which performs it for you with crossbrowser ability.

example :

// Store current user
store.set('user', { name:'Marcus' })

// Get current user
store.get('user')

// Remove current user
store.remove('user')

// Clear all keys
store.clearAll()

// Loop over all stored values
store.each(function(value, key) {
    console.log(key, '==', value)
})

回答8:

Session storage cannot support an arbitrary object because it may contain function literals (read closures) which cannot be reconstructed after a page reload.