JsonStorage

A light, sensible abstraction for DOMStorage (such as localStorage).

Installation

Bower (Browser)

bower install json-storage
# or
wget https://git.coolaj86.com/coolaj86/json-storage.js/raw/branch/master/json-storage.js

Node.JS (Server)

npm install -S localStorage json-storage

Usage

Made for Node.js and Bower (browser-side).

var localStorage = require('localStorage')
  , JsonStorage = require('json-storage').JsonStorage
  , store = JsonStorage.create(localStorage, 'my-widget-namespace', { stringify: true })
  , myValue = {
        foo: "bar"
      , baz: "quux"
    }
  ;

store.set('myKey', myValue);
myValue = store.get('myKey');

NOTE: When using with Node and the localStorage module, you may wish to pass the { stringify: false } option to prevent double stringification.

API

• JsonStorage.create(DOMStorage, namespace, opts)
  • DOMStorage should be globalStorage, sessionStorage, or localStorage. Defaults to window.localStorage if set to null.
  • namespace is optional string which allows multiple non-conflicting storage containers. For example you could pass two widgets different storage containers and not worry about naming conflicts:
    • Gizmos.create(JsonStorage.create(null, 'my-gizmos'))
    • Gadgets.create(JsonStorage.create(null, 'my-gadgets'))
    • Namespacing can be turned off by explicitly setting false
      • Gadgets.create(JsonStorage.create(null, false))
  • opts
    • stringify set to false in node to avoid double stringifying
• store.get(key)
• store.set(key, value)
• store.remove(key)
• store.clear()
• store.keys()
• store.size()
• store.toJSON()
• JSON.stringify(store)

NOTE: You cannot omit optional parameters. Use null if you want accepts the defaults for some things and provide a values for others. For example: JsonStorage.create(null, null, { stringify: false })

JSON / DOMStorage Conversion Gotchas

These notes do not reflect a bugs or defects in this library, they're simply to inform you of a few 'gotchas' inherent in JSON / DOMStorage conversion.

99.999% of the time these gotchas shouldn't effect you in any way. If they do, you're probably doing something wrong in the first place.

undefined vs null

It is not valid to set undefined in JSON. So setting a key to undefined will remove it from the store.

This means that store.set('x') is the same as store.remove('x').

To save undefined, use null instead.

Note that both values that exist as null and values that don't exist at all will return null.

store.set('existing-key', null);
null === store.get('existing-key');
null === store.get('non-existant-key');

null vs "null"

The special case of null as "null", aka "\"null\"":

typeof null        // object
typeof "null"      // string
typeof "\"null\""  // string

null, and "null" both parse as null the "object", instead of one being the string (which would be "\"null\"").

JSON.parse(null)       // null (object)
JSON.parse("null")     // null (object)
JSON.parse("\"null\"") // 'null' (string)

Objects containing null, however, parse as expected { "foo": null, "bar": "null" } will parse as foo being null but bar being "null", much unlike the value "null" being parsed on its own.

JSON.parse('{ "foo": null }')    // { foo: null }
JSON.parse('{ "foo": "null" }')  // { foo: 'null' }