What happens when you use RxJS in React?

3 min readJan 30, 2017

Update (02.02.2019): more than two years ago, while experimenting with RxJS and React, I’ve created a library presented in this post. Please note that in the meantime, that library was deprecated.

Using observables seems like a good thing. So why don’t we use it in React apps more often?

With observables we can easily manage asynchronous data streams, but what is a stream in a React component?

Streams in React

To determine this, let’s start by analyzing a simple ClickCounter example:

Simple React ClickCounter component

This is a component describing asynchronous behavior. On every click event on a button tag, the state is changed. Or in other words, the state changes as a result of events happening over time.

A sequence of ongoing events ordered in time is a definition of a — stream.

So, instead of defining this.state as an object which will later be overwritten, we can define it more declaratively:

Defining state as a stream

Managing component streams

However, even when defined like this, how will our component know when to update? Somebody still has to invoke this.setState() .

There are some existing solutions for achieving this, but it seemed a bit too complicated to me.

Other more popular options for using “Functional Reactive paradigm” requires you to use another framework or another programming language (like Cycle.js or elm).

But I didn’t like the idea of losing all good things React offers you.

So, I created a small library called Recycle, which is my attempt at solving this issue. It converts “functional/reactive object description” into a React component.

Here is how a ClickCounter looks like when defined using Recycle:

It works by “monkeypatching” React.createElement. Before a component is rendered, if a select query is matched with node element, recycle sets inline event listener defined inupdate function.

Each time event handler dispatches an event, it calls selectedNode.rxSubject.next(e)

In short, Recycle creates a classical React component out of this object by creating inline event handlers and handles component local state by using “Redux style” reducer operator.

Pros

Greater separation of concerns between component presentation and component logic.

Classical React component — mixing logic and structure

You don’t need classes so each part of a component can be defined and tested separately.
Component description is more consistent. There is no custom handleClick events or this.setStatestatements that you need to worry about.
State is calculated the same way as for redux store: state = reducer(state, action).
Redux container looks like a normal component and it’s more clear what it does.
Easy to use in an existing React application (choose components which you wish to convert).

Cons

Observables. They come with trade-offs.
You don’t like the idea of selecting nodes using class names, ids or tags
Yo need to use advanced React API (like forceUpdateor shouldComponentUpdate)
Yo need direct access to DOM elements (using this.refs) for external plugins or similar

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