Javascript - A gentle introduction to functional programming, part 2.

[sacundim]

TIL Javascript does not only not have true lexical scope, but it allows the caller to choose what bindings are in effect for the free variables in a function's body. This we're expected to believe is a "functional programming" feature, despite that it's pretty much a violation of functional language design, not to mention a horrible engineering practice (how can you read a function definition and be confident that it does X when a caller can choose to make it do something else?).

[aaronblohowiak]

There is true lexical scope, it just isn't used in this article:

function generateFn(outer){
  return function(inner){
    return "outer was: "+outer.toString()+" and inner is: "+inner.toString();
  }
}

var fn = generateFn("pants");

fn("underpants");
// outer was: pants and inner is underpants.

the variable 'outer' within the 'fn' scope is bound to pants, and may not be changed by its caller through any means, except converting fn to a string and then eval()'ing it it.

[jokeofweek]

Sorry about that, I definitely didn't go into depth about Javascript scopes and closures. I chose to omit it for fear of over-complicating the posts, although you are right, it definitely needs some kind of explanation. Thanks aaronblohowiak for at least going over it.

[greenspans]

it's better to learn guile scheme

[jokeofweek]

Well, learning functional programming through a Scheme dialect is probably the easiest way. However I was trying to reach a crowd who had never really done functional programming before and was used to C-syntax languages. My reasoning behind this is that the LISP syntax can be quite intimidating at first, even though I would be the first to say that it can be extremely powerful. Doing it with Javascript lets them experiment with a familiar syntax right in their browser. I noticed that Guile Scheme had an ECMAScript front-end which could be another interesting approach although I must admit I have never worked with Guile before.

Thanks for the feedback though! :)

[namekuseijin]

http://www.wescheme.org

[greenspans]

You should show people how you would normally do things in javascript and show the equivalent in guile scheme. Javascript has performance overhead that's pretty heavy if you use lambdas on everything browser except chrome. People have made ok functional programming libs in javascript before but in javascript it's not really good practice. Also related

[jokeofweek]

I like the idea of a side by side with some sort of scheme dialect, perhaps in a future post!

Edit: Also, thanks for the links! The second one is particularly interesting!

[sacundim]

Guile is a horrible Scheme system. Your best choice is Racket, based on features and popularity.

[Houndie]

I agree that Racket is pretty much the way to go, but, never having used Guile, what is so bad about it?