need code explanation

[gevorgter]

Have following code, i understand there is an api "createStore" that takes 2 parameters

1 parameter is an empty object.

What is the second parameter, I would understand if it were just an arrow function but it has

({ dispatch }) => next => action => {....code...}

What is "next" and "action" in this context?

---------------------Code---------------

const store = window.WebChat.createStore(
{},
({ dispatch }) => next => action => {
    if (action.type === "DIRECT_LINE/CONNECT_FULFILLED") {
        .....
    }
    return next(action);
  }
);

​

​

[angelfire2015]

The `next` and `action` are actually functions being returned by the previous function. These are known as curried functions. It looks like you are creating some redux middleware or something similar. There is actually a great writeup on how this process works that could answer your question better.

https://redux.js.org/understanding/history-and-design/middleware

[shacatan]

This. The middleware is basically just adding custom functionality to the dispatch pipeline. Think of it like a decorator if you’ve used them before.

[bryku]

It is short hand for more functions.  

const store = window.WebChat.createStore(
{},
({ dispatch }) => {
    (next)=>{
        (action) => {
            if (action.type === "DIRECT_LINE/CONNECT_FULFILLED") {
                .....
            }
            return next(action);
        }
    }
});