locustjs-storage
This library presents storage in an abstract way. It provides an abstract StorageBase
class and wrappers around localStorage
and sessionStorage
as implementations of the base abstract StorageBase
class.
The aim of the library is loose coupling and decoupling an application dependency on a specific storage.
The abstraction provided by this library enables us to define storages other than localStorage
or sessionStorage
that are able to store non-string items.
Abstraction
StorageBase
This is the main abstract storage class that defines structure of all storage classes.
Public Methods
method | description |
---|---|
getItem(key):any |
Retrieves an item from storage by its key |
setItem(key, item):void |
Saves an item in storage by its key |
clear():void |
Clears storage and removed all items. |
removeItem(key):void |
Removes an item from storage by ites key. |
containsKey(key):bool |
Checks whether an item exists in the storage or not. |
keyIndex(key):number |
Returns back index of an item in the storage by its key. |
key(index):string |
Returns back key of an item at given index. |
keys():string[] |
Returns back all items' keys. |
Public Properties
property | type | description |
---|---|---|
length |
number |
Returns the number of items in storage. |
Protected Methods
Sub-classes should override and implement these methods.
method | description |
---|---|
serialize(item):any |
Should serialize an item in a format suited to current storage. It is called automatically by setItem() . Sub-Classes should override this method based on their own business. |
deserialize(item):any |
Should deserialize an item stored in the current storage. It is called automatically by getItem() . Sub-Classes should override this method based on their own business. |
_getItem(key) |
This method should return the actual item stored in the storage by its key. |
_setItem(key, value) |
This method should perform the actual saving of given item into the storage by its key. |
Using serialize/deserialize
methods enables us to define sub-classes to perform operations other than just serializing or deserializing values. For example, we can define classes to automatically encrypt/decrypt
or compress/decompress
items in the storage before storing and after retrieving them.
Implementations
locustjs-storage
provides 6 sub-classes for StorageBase
.
Sub-Class | Description |
---|---|
InMemoryStorage |
Uses memory as the storage. |
LocalStorage |
This is a wrapper around window.localStorage . It works the same as window.localStorage but supports only string items. |
SessionStorage |
This is a wrapper around window.sessionStorage . It works the same as window.sessionStorage but supports only string items. |
Note 1:
There is also a helper abstract class named ProxyStorage
that is intended to work both with window.localStorage
and window.sessionStorage
.
Note 2:
LocalStorage
and SessionStorage
classes enables us to support storing items in a format different than the ordinary string
type such as JSON
. This is how the two following classes are defined.
Sub-Class | Description |
---|---|
LocalStorageJson |
This class derives from LocalStorage and by overriding serialize and deserialize method, supports objects as well and is not limited to store only string values like localStorage . It serializes/deserializes items in JSON format automatically. |
SessionStorageJson |
This class derives from SessionStorage and by overriding serialize and deserialize method, supports objects as well and is not limited to store only string values like sessionStorage . It serializes/deserializes items in JSON format automatically. |
Examples
const store = new LocalStorageJson();
store.setItem('key1', 'test'); // storing a string
store.setItem('key2', 23); // storing a number
store.setItem('key3', { name: "John Doe", age: 24 }); // storing an object
store.setItem('key4', [10, 20, 30]); // storing an array
console.log(store.length); // 4
console.log(store.containsKey('key2')); // true
console.log(store.containsKey('key6')); // false
console.log(store.keyIndex('key3')); // 2
console.log(store.key(3)); // key4
console.log(store.keys()); // [ "key1", "key2", "key3", "key4" ]
console.log(store.getItem('key1')); // 'test'
console.log(store.getItem('key2')); // 23
console.log(store.getItem('key3')); // { name: "John Doe", age: 24 }
console.log(store.getItem('key4')); // [10, 20, 30]
store.clear();
console.log(store.length); // 0