Debug Functional Compositions with a Logging Side Effect in JavaScript

In the last example, why is the root map wrapped in a compose?

Hey Haroen, you are correct that the final output could be refactored one step further by removing the outer compose since we're only passing one argument to compose. In truth, it just didn't occur to me at the time to take it that one step further. Fortunately, there's nothing mathematically invalid about having a redundant compose this way. Good catch.

Now, just to be clear to others, if they didn't understand what took place in that final step, because our composition was three maps over individual functions, we could compose those individual functions into a new function and pass that into a single map.

So what starts as:

const slugify = compose(
  map(join('-')),
  map(split(' ')),
  map(lowerCase)
)

Can be:

const slugify = map(compose(join('-'), split(' '), lowerCase))

Thanks, that makes sense!

Thanks so much Kyle, this was a nice and comprehensive course At this point, if you guys want to know a little more about functional programming I recomend you the free book 'Mostly adequate guide to FP (in javascript)' https://github.com/MostlyAdequate/mostly-adequate-guide

Hi Kyle, very helpful course, can you explain what is the feature you used as (console.log(msg, x), x) . Why does this returns the x after comma?

Hey Hakan, good question I was also wondering, check out this: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comma_Operator

Hi Kyle, very helpful course, can you explain what is the feature you used as (console.log(msg, x), x) . Why does this returns the x after comma?

Hi Hakan, we need "x" param after console.log to pass forward "x" value through the composition since the console.log just log the value and nothing to return

Hey Hakan, good question I was also wondering, check out this: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comma_Operator

Hi Hakan, we need "x" param after console.log to pass forward "x" value through the composition since the console.log just log the value and nothing to return

Thanks Kostiantyn and Florian, didn't know about this comma operator.

Thanks Kyle! Really a good explanation of how to use functional programming. I have read a lot about it, and this goes from theory into practice. It would be great to see more, like examples of implementation in a web app.

Thoroughly enjoyed the course. Every example was simple, very clean and easy to understand. Comma operator and point-free programming were two interesting things that I learned apart from the core JS functional concepts! Loved it.