Reactive programming is mostly like Functional programming where functions and data are combined with time and called streams. We can create a stream from anything: array, primitive value, etc. We can merge streams, composite them, have HoS (high order stream) which takes another stream as an input or gives as a result.

A stream is a sequence of ongoing events ordered in time. Streams can emit three things: a value (of some type), an error, or a "completed" signal. To capture these emits you subscribe to a stream passing a function called observers (Observer design pattern).

On top of that ideas, we have a bunch of functions to help us handle streams with all the power of functionality.

The most common example of RP in the JavaScript world is RxJS.

Pros:

• writing declarative code
• avoiding callback hell
• purity
• avoiding implementation details with a focus on business goals

Cons:

• only hard debugging
• making documentation
• memory consumption,
• time to start
• managing concurrency
• complexity of testing
• a learning curve

• The introduction to Reactive Programming you've been missing