todo.txt

* isEmpty():
    - to check if the cache store is empty or not.
    - if pass the key to it will check the value of this key.
    - params: (key => string, not required)
    - return: (boolean)
    - data.isEmpty() => true / false
    - data.isEmpty('key') => true / false

* has():
    - to check if specific key is exist or not.
    - params: (key => string, required)
    - return: (boolean)
    - data.has('key') => true / false

* keys():
    - to return all keys used in the data cache store.
    - params: none
    - return: (array of string)
    - data.keys() => ['key 1', 'key 2', ...]

* values():
    - to return all data cached.
    - params: none
    - return: (any)
    - data.values() => ['name'], 'name', [{name: 'name'}], false...

* clear():
    - to clear all data in cache store
    - if pass key to it will clear data for this key store
    - params: (key => string, not required)
    - return: void
    - data.clear()