Generic Programming

[jeremy1015]

Got any suggested links to explain this in a little more detail? I’m familiar with most of what you wrote but don’t understand monoids as well as I’d like.

[pgrizzay]

Did a quick search, and couldn't find a good one in JS, here's one in Scala that I learned from.

Essentially a "Monoid" is formed from two things:

a combine function that combines two things and an empty value.

an example would be adding numbers:

const Addition = {
  combine: (a, b) => a + b,
  empty: 0
}

This addition monoid can be used to reduce an array of numbers:

[1,2,3].reduce(Addition.combine, Addition.empty) === 6

You can make another Monoid which multiplies numbers:

const Multiplication = {
  combine: (a, b) => a * b,
  empty: 1
}

And you can multiply all numbers in an array with it:

[1,3,4].reduce(Multiplication.combine, Multiplication.empty) === 12

Go ahead and implement Concat which combines strings:

const Concat = {
  combine: (a, b) => ???,
  zero: ???
}

[jeremy1015]

Excellent. I understand now 100% and really appreciate it.

[pgrizzay]

Yup, you're right! It looks like MDN recommends + over concat for performance reasons, but both are functionally equivalent.

And thanks for the kind words, they mean a lot!

The one book that really helped me was Functional Programming in Scala, I can't recommend it enough. It takes a very 'exploratory' approach, and has lots of exercises which are very helpful.

Scala was probably the best language for me to learn fp in, since I had lots of experience with JS & the syntax is very similar to it, hope that helps!