Introduction
An Observable is simply an asynchronous stream of data to which we may subscribe and unsubscribe.
You already use such streams: event listeners, ReadableStream, setInterval, Promises, and many more... are all streams.
Observables give you powerful tools to create and organise these streams, while managing cancellation of complex data pipelines like a breeze.
🔬 However, learning Observables is hard, which is discouraging, due to their steep initial learning curve. But, once done, when you'll understand the core concepts of Reactive Programming, you'll use them effortlessly in you day-to-day code, gain in productivity, quality of code, and create more robust applications.
When I started using RxJS (the most used Observables library) it was a nightmare: it lacked tutorials, the documentation was cryptic, and I couldn't find concrete use cases and examples. It's just a pile of documentation where the authors expect that everyone can read their mind 😑.
But now, that I'm very confortable with Reactive Programming, I simply cannot work without it: it solves so many problems and allows me to create very consistent applications.
The first thing to know is that Reactive Programming requires you to think reactively. Just like writing Promises was a different paradigm with regards to non-blocking code (async thinking), in the same way, you'll have to be able to change your perspective on variables and streams.
So the first question to answer is: when should I use an Observable ? Well, the correct answer is: everytime you have a value which will evolve through time. It may be a user's input, an async HTTP request, a computed value, a stream of data, etc.
If you force yourself to use the Observables when you encounter these situations, then you'll quickly become an Observables' master.
The second and most important point: you'll have to be patient, read the documentation and learn at least the essentials functions before beginning. Just like you would have done for a tooling library like lodash or underscore. Don't jump immediately into coding. Take an hour (or more), and read progressively this tutorial. If you skip this step, you'll feel frustrated and limited while creating your pipelines, so, you won't be able to unleash the true potential of Observables.