Get started with functional programming in JS through this  series of explainers & interactive exercises. 

To access the full workshop, including video lessons, join FrontendMasters: frontendmasters.com/workshops/functional-first-steps

Anjana Vakil

Functional JavaScript First Steps

What is functional programming?

Exercise: Pure Functions

Staying out of the loop with recursion

Exercise: Iteration vs. Recursion

Flying first class with  higher-order functions

Exercise: Filter, Map, Reduce

Getting closure

Exercise: Closures & Currying

It's functions all the way down

Exercise: Function Composition

Immutability

Exercise: Avoiding mutation

Recap & takeaways

Next steps

Workshops using Observable for hands-on exercise materials

Workshops

But isn't referring to the new Date constructor making this impure? 🤔

Kartik Maurya

Hi Kartik, you're totally right that the new Date constructor introduces complexity that could potentially lead to impurity. But in this case, because of how Date works and the values we're passing in, we reasonably expect that every time we call this function, we will get the same output (i.e. it's deterministic). So for the purposes of this exercise, we can consider getWorkshopDate pure - although if e.g. someone went and changed the implementation of Date, such that calling it like this would not give a deterministic result, that could change! So your instinct that there's something a little weird here that could potentially make it impure is right :) Hope that helps!

That helps, thanks for the clarification :)

Awesome, no worries & sorry for the slow reply!