Most of the devs possibly start their careers using imperative programming. It’s the most common paradigm, hands-down. A strong opposition to this paradigm is the functional programming or just FP.
The functional programming works based on the concept of data immutability and on mathematics expressions where each pure function has a particular return that can be used as param by another pure function.
Broadly adopted in the academic universe, FP has also started to gain territory in a professional context.
Even though the final outcome will be pretty much the same, these two paradigms are so different from each other that this can largely impact the workflow and the code maintenance.
One of the best ways to explain the FP is to compare it with the imperative paradigm.
In the imperative programming the dev writes the code as a sequence of orders so the system behaves as expected. The software will then execute the predefined actions as it should.
Functional programming is quite different in this regard, since the dev should write the functions and the software will work based on the interact built by these functions. The result of a function will become an important param of another function and the cycle goes on.
It also generates a code that is easier to read, maintain, and brings many features to the devs. It doesn’t happen to the important paradigm, where a single change can create unnecessary repetitions or incongruities. FP also provides a better and smoother experience with tests and debugging due to the fact the functions are more isolated and simpler to be evaluated.
The bad part about FP, is that it can be harder to assimilate in a first moment. Also, it can be more difficult to estimate deadlines making the management process more challenging than the imperative model.