A angular storage object to persistent data

AngularStorage.js

/**
*
*/
$rootScope.storage = function () {
    /**
    *   Set default API
    **/
    this.API = window.sessionStorage;
    /**
    *   Set localStorage API
    */
    this.enablePersistence = function() {
        this.API = window.localStorage;
        return this;
    };
    /**
    *   get current API
    */
    this.getPersistence = function() {
        return this.API;
    };
    /**
    *   Check if item is Empty.
    *   Note: If the item don't exists, return true
    *
    *   Example:
    *   if ($scope.storage.isEmpty('item')) {
    *       console.log('Is empty!');
    *   }
    *
    */
    this.isEmpty = function (key) {
        var mixedVar = this.API.getItem(key);
        var undef
        var key
        var i
        var len
        var emptyValues = [undef, null, false, 0, '', '0']
        for (i = 0, len = emptyValues.length; i < len; i++) {
            if (mixedVar === emptyValues[i]) {
                return true
            }
        }
        if (typeof mixedVar === 'object') {
            for (index in mixedVar) {
                if (mixedVar.hasOwnProperty(index)) {
                    return false
                }
            }
            return true
        }
        return false
    };
    /**
    *   Check if item exists
    *
    *   Example:
    *
    *   if ($scope.storage.exists('item')) {
    *       console.log('The item key exists on storage');
    *   }
    *
    *   if ($scope.storage.exists(['a', 'b', 'c', 'd'])) {
    *       console.log('A + B + C + D exists on storage');
    *   }
    *
    *   $scope.storage.exists({'existsA':'a', 'existsB':'b', 'existsC':'c', 'existsD':'d'});
    *   // output:
    *   // {'existsA':true, 'existsB':false, 'existsC':false, 'existsD':false}
    *
    */
    this.exists = function (nested) {
        if (angular.isArray(nested)) {
            for (var i = 0; i < nested.length; i++) {
                if (this.API.getItem(nested[i]) === null) {
                    return false;
                }
            }
            return true;
        } else if(angular.isObject(nested)) {
            var results = {};
            for (index in nested) {
                results[index] = this.API.getItem(nested[index]) !== null;
            }
            return results;
        } else {
            return this.API.getItem(nested) !== null;
        }
    };
    /**
    *   Return all items
    *   Example:
    *
    *   $scope.storage.all();
    */
    this.all = function() {
        return this.API || {};
    };
    /**
    *   Set a new item(s)
    *   Example:
    *
    *   # Define only key(by default value is undefined)
    *   $scope.storage.set( 'a' ); // value is 'undefined'
    *
    *   # Define key and value as int, float, object, null, string, array, boolean, function
    *   $scope.storage.set( 'a', 1 );           // value is integer
    *   $scope.storage.set( 'a', 1.2 );         // value is float
    *   $scope.storage.set( 'a', "1" );         // value is string
    *   $scope.storage.set( 'a', { a: 1 } );    // value is object
    *   $scope.storage.set( 'a', [1,2,3] );     // value is array
    *   $scope.storage.set( 'a', null );        // value is null
    *   $scope.storage.set( 'a', true );        // value is boolean
    *   $scope.storage.set( 'a', false );       // value is boolean
    *   $scope.storage.set( 'a', function(){}); // value is function
    *
    *   # Store multiple items at same time with a object
    *   $scope.storage.set({
    *       a:  1,
    *       b:  true,
    *       c:  "hi",
    *       d:  function() {},
    *       e:  0.2
    *   });
    */
    this.set = function () {
        try {
            if (arguments.length == 0) {
                throw "need key";
            }
            var key = arguments[0],
                value = undefined;
            if (arguments.length > 1) {
                value = angular.toJson(arguments[1]);
            }
            if (angular.isObject(key)) {
                for (index in key) {
                    this.API.setItem( index, angular.toJson(key[index]) );
                }
                return true;
            } else if (!this.exists(key)) {
                return this.API.setItem( key, angular.toJson(value) );
            }
        } catch (e) {
            return false;
        }
    };
    /**
    *   Get a item
    *   Example:
    *
    *   # Get value from a item
    *   $scope.storage.get('a'); // return value from key 'a'
    *
    *   # Get items form array
    *   $scope.storage.get(['a', 'b'])
    *   // output:
    *   // [1]
    *
    *   # Return items from dictionary
    *   $scope.storage.get({
            name    :   'a',
            country :   'b',
            language:   'c'
    *   });
    *   // Output:
    *   // {name: 'Olaf', country: 'Chile', language: 'spanish'}
    */
    this.get = function(key) {
        if (angular.isObject(key)) {
            var result = {};
            for (index in key) {
                result[index] = angular.fromJson(this.API.getItem(index));
            }
            return result;
        } else if (angular.isArray(key)) {
            var result = {};
            for (var i = 0; i < key.length; i++) {
                result[i] = angular.fromJson(this.API.getItem(index));
            }
            return result;
        }
        return angular.fromJson(this.API.getItem( key ));
    };
    /**
    *   Remove a item(s)
    *   Example:
    *
    *   # Remove a item
    *   $scope.storage.remove('a');
    *
    *   # Remove multiple items
    *   $scope.storage.remove(['a', 'b', 'c'])
    */
    this.remove = function (key) {
        if (!this.exists(key)) {return false;}
        return this.API.removeItem(key)
    };
    if (arguments.length == 0) {
        return this;
    } else if (arguments.length == 1) {
        if (angular.isArray(arguments[0]) || angular.isObject(arguments[0])) {
            return this.exists(arguments[0])
        }
        return this.get( arguments[0] );
    } else if (arguments.length > 1) {
        return this.set( arguments[0], arguments[1] );
    }
};

$rootScope.storage = $rootScope.storage();

API:

• exists( mixed )
• set ( mixed )
• remove ( mixed )
• get ( mixed key )
• all ( void )
• isEmpty ( mixed key )