use localStorage

annotated.js

function(
  a, // placeholder for storage object
  b  // placeholder for JSON
){
  return b
    ? {                 // if JSON is supported
      get: function(    // provide a getter function
        c               // that takes a key
      ){
        return a[c] &&  // and if the key exists
          b.parse(a[c]) // parses and returns it,
      },
      
      set: function(     // and a setter function
        c,               // that takes a key
        d                // and a value
      ){
        a[c] =           // and sets
          b.stringify(d) // its serialization.
      }
    }
    : {}                 // if JSON isn't supported, provide a shim.
}(
  this.localStorage // use native localStorage if available
  || {},            // or an object otherwise
  JSON              // use native JSON (required)
)

index.js

function(a,b){return b?{get:function(c){return a[c]&&b.parse(a[c])},set:function(c,d){a[c]=b.stringify(d)}}:{}}(this.localStorage||{},JSON)

LICENSE.txt

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
                    Version 2, December 2004

 Copyright (C) 2011 Jed Schmidt <http://jed.is>

 Everyone is permitted to copy and distribute verbatim or modified
 copies of this license document, and changing it is allowed as long
 as the name is changed.

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

  0. You just DO WHAT THE FUCK YOU WANT TO.

package.json

{
  "name": "storage",
  "keywords": ["localstorage", "storage", "store"]
}

function(a,b){return function(c,d){return d==null?a[c]&&b.parse(a[c]):a[c]=b.stringify(d)}}(this.localStorage||{},JSON)

ls('foo', {
  bar: 'bar'
});

ls('foo'); // => { bar: 'bar' }