Just read Real World Haskell and do all the exercises. After you really understand functor and applicative, and do all the exercises, monad will not be much more complicated.
After you learn the math, that is, the algebraic structure that is called a monad (after, not before) you can watch a few YouTube videos and read some tutorials, until you find the wavy-handy explanation that makes more intuitive sense to you, personally.
I don't know of any to be honest, and I would seriously just avoid all of them. Read the fantasy land spec (functions + laws and how it's implemented) instead, and ask questions on an FP channel if you're stuck or confused
I've heard 'Professor Frisbee's Mostly Adequate Guide to Functional Programming' is ok, but I'm looking at the section on monads and the monad laws aren't even mentioned. Which is a huge red flag for me, because without the laws it isn't a monad and you can get really strange behavior if you use it like that. I would avoid reading that book
People write these tutorials because they want to improve their portfolio to further their career, but they often don't even understand it yet -- a perfect example of a perverse incentive.
An example is the guy who wrote "You Don't Know Js" [1]. All of these are completely wrong statements:
- "But what I will say is that a monad is basically a value type."
- "A monad is a data structure. It's a type."
- "Actually, a monad isn't a single data type, it's really more like a related collection of data types. It's kind of an interface that's implemented differently depending on the needs of different values. Each implementation is a different type of monad."
- Says "methods" a bunch of times, there are no methods involved with monads in any way, it's FP
- His example in "Just a Monad" isn't a monad
- "Actually, the Maybe monad is a particular pairing of two other simpler monads: Just and Nothing"
- "Many implementations of a JavaScript Maybe monad include a check (usually in map(..)) to see if the value is null/undefined, and skipping the behavior if so" - that makes it not a monad, it violates the laws. Java's Optional type isn't a monad for similar reasons
- "But... that approach to Maybe is not a pure monad." - there's no pure/impure monads, it's either a monad or it isn't
- "The core spirit of a Monad says that it must be valid for all values and cannot do any inspection of the value, at all -- not even a null check. So those other implementations are cutting corners for the sake of convenience. It's not a huge deal," - It is a huge deal, a whole lot of abstractions are built on top of monads, if it doesn't satisfy the laws exactly then you'll be entering a world of pain you really wish you didn't
I stopped reading the rest but you get the point. You don't want to end up in a situation where you have to unlearn a bunch of this stuff. Btw the guy who wrote the Professor Frisbee book wrote the foreword in this book, so you can see why a lot of this stuff raises red flags for experienced FPers. My suggestion is to read fantasy land and ask questions on an FP channel
After you learn the math, that is, the algebraic structure that is called a monad (after, not before) you can watch a few YouTube videos and read some tutorials, until you find the wavy-handy explanation that makes more intuitive sense to you, personally.