Redux is a library which is used to maintain a state of the application at an application level, it reduces the complexity of managing different states of the components when the app is getting comparatively larger, it provides the privilege to maintain a state of different components efficiently.

1. Basic Fundamentals of Redux
Redux is a library which is use to maintain state of the application at application level , it
reduces complexity of managing different states of the components when app is getting
comparatively larger , it provides the privilege to maintain state of different components
efficiently.
Redux works on three basic principles
1)“Single source of truth” – It means that there is only one store having giant object called
application state for the entire application which resides in the store.
2) State is read only – The only way to change the state is dispatching an action.
3) Changes are made with pure function ie. reducer – Dispatched action will be received by the
reducer which modify the state in the store if required.
Action:
An action is a plain javaScript object with one mandatory field called ‘type’ with the provision of
another fields, whenever we need to change or modify state in the store, need to dispatch an
action
Reducer:
Reducer is nothing but just a pure function.which produces state out of action and whatever
reducer returns will become state of the application.
Pure Function is a function which doesn’t allow mutation of the data which is passed as the
argument and if any modification is done it always returns new data in place of modifying the
existing data, there should not any API Calls or any method calls, just a pure javaScript object
that takes input as an argument and return something.

2. Reducer called with two argument , first is current state and second is action, that dispatched
before, now reducer will filter out action and produce some amount of data as a state.and that
state is going to persist in the store ,in this example if the user tries to login ,dispatching and
action , and that action go though all the different reducer and persist state or saving the
credential to the store.
Store:
Store holds application, we can think it as an object tree, store allows to access the state via
getState() and gives us current state of the application method and also allow change within
the store by dispatch() method.
Redux library gives a method createStore() which takes reducer as a argument by which state
of the store is going to be changed.
so basically redux is all about managing state , all we need to do is dispatching an action, it
goes all the different reducer, reducer produce some amount of data as state in store.