Simple Angular Database - JSON in LocalStorage as a service

db.coffee

###
This dead-simple service just returns a javascript object called "Db",
which comes with two functions built in: save() and clear(). 
Save attributes directly onto the object, then call Db.save(), and it 
will be written into localstorage.

Sample usage:

angular.module("my_app").controller "HomeCtrl", (Db) ->
  $scope.user = Db.user || {};
  
  $scope.updateUser = ->
    Db.user = $scope.user
    Db.user.updated_at = new Date()
    Db.save()
    
  $scope.logout = ->
    Db.clear()

caveat: Since functions can't be JSON-stringified, don't store functions 
inside the Db object.

###

angular.module("my_app").service "Db", ->
  db = window.localStorage.getItem "my_app_database"
  db = if db? then JSON.parse(db) else {} 
  
  # Set any default settings here, if needed
  db.defaultKey or= "defaultValue"

  db.save = ->
    window.localStorage.setItem "my_app_database", JSON.stringify(db)

  db.clear = ->
    for key, val of db
      delete db[key] if db.hasOwnProperty(key) and key isnt 'save' and key isnt 'clear'
    db.save()

  return db

Should really wrap in try/catch block because of possible exceptions: https://gist.github.com/drGrove/599fd38f509a439825b2