Pure functions concept was a breakthrough for me too. As a design pattern they are wonderful, there is so much less mental context to keep track of. Now whene

Pure functions concept was a breakthrough for me too. As a design pattern they are wonderful, there is so much less mental context to keep track of. Now whenever I see mutated variables and class attributes, or random side effects besides reading/writing to a database, it kinda makes me cringe and think it's a "oh here we go" into a rabbit hole just to understand what the code is doing. 9/10 the code does what it's supposed to, but the mutations and side effects makes understanding and extending it so much harder.