Why do we need Flux with React?

In theory you don't need flux. In small applications you don't need flux for sure.But what if your application consist of hundreds components? And one of your component is form. User populate this form and you send its content to server. And get response from server with new data.And assume that this response data and data from form are necessary to other components.

1. Without flux:You can move your data to root component and then distribute it down to all components. But if you need to distribute data from many other components too? This makes your application very complex.

2. with flux:You move your data to stores, and all components which are interested about this data, can get it from there. You have better control on your application and source data.

I prefer redux (only one store and one source of truth)

edit:

Why is React called as a view library even if it can handle application state?

MVC is a software architectural pattern. It divides a given software application into three interconnected parts (models, views, controllers).If we think about react and MVC it fit as View. But this is nothing wrong. It doesn't mean that you can use it only for views. It allows you to create normal applications.

But in other hand you can use it as view for other frameworks (for example you can use it with angular).

In other words it is very flexible library for many uses.

You don't NEED Flux the same you don't need MVC. They are both architectures and you can of course build something without using either.

Would you build a non-MVC app in 2016? Probably not, that doesn't mean that people didn't do it in the past.

Flux is awesome! But as most things in the tech industry is not always the right decision, things vary in a project requirement basis.

Probably the biggest selling point of Flux is that it tries to enforce the data flow in one direction, this means that you know for sure where the data is coming from. In a non-flux app the data for a component could be an own property, a property passed down the component tree, a local state variable, a state variable result of calling an API.

With Flux: "where does the data come from?". Answer: from the stores. Redux takes this further and only uses a single store.

Flux has been criticized because you need a lot of boilerplate code but again is a matter of tradeoffs.

At the end is always your call depending on your project needs.