**Thunk** is a middleware for Redux. 

To understand this, let's see what Redux is in the first place. **Redux** is a JavaScript library for managing application state. It has a few key concepts like: 

* 'actions' 
* 'action creators'
* 'reducers' 
* 'dispatch'  
* 'middleware' 





We won't dive into the details, but just know that actions contain information that is dispatched to reducers. The middleware sits between the dispatch and reducers.

The Redux middleware provides a third-party extension point between dispatching an action and the moment it reaches the reducer.  

Thunk is one such middleware that allows you to write action creators that return a function instead of an action. This interception of actions before reaching the reducers enables you to incorporate logic like, "delay the dispatch of action" or "only dispatch if a certain condition is met."

# Installation
``` cmd
npm install redux-thunk
```

## Example

Below, an action creator returns a function to perform conditional dispatch.  
The function `printWelcomeIfNewUser()` wraps the function `printWelcome()` and adds logic, dispatch `printWelcome()`, but only if the `isNewUser` state is true.

function printWelcomeIfNewUser() {
  return (dispatch, getState) => {
    const { isNewUser } = getState();
 
    if (!isNewUser) {
      return;
    }
 
    dispatch(printWelcome());
  };
}


What is Redux Thunk?

We won t dive into the details, but just know that actions contain information that is dispatched to reducers. The middleware sits between the dispatch and reducers. The Redux middleware provides a third-party extension point between dispatching an action and the moment it reaches the reducer. Thunk is one such middleware that allows you to write action creators that return a function instead of an action. This interception of actions before reaching the reducers enables you to incorporate logic like, “delay the dispatch of action” or “only dispatch if a certain condition is met.” 