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Marc Fogleman

I have an applySpec and Promise problem

I am calling a database, getting back the document. I need to do a bunch of transforms based off the data gotten back, so I'm using an applySpec. It works great. But one of the fields in my spec needs to make a GET request to another server, and get the response. applySpec does not wait on promises. I figure there are 4 possible solutions

  1. There is a combination of wrapping this in async/awaits and R.then, to make this wait on the result, and I just dont know what it is
  2. This is a terrible anti pattern that I shouldnt be using at all
  3. Someone wrote a utility to solve this exactly (I found promise-apply-spec, but I think it may be a bit heavy for what I want)
  4. I'm going to need to hand roll either my own version of applySpec, or wrappers to handle this

If anyone has more experience in this or similar issues, feedback and guidance is appreciated

Ben Briggs
@MFogleman You could also look into using a lazy data structure e.g. https://github.com/fluture-js/Fluture - not sure how well it would work with applySpec though to be honest
i have a common paradigm, wondering if this has a functional term and maybe has a ramda function for it. I frequently do something like this: myObject[key] = myObject[key] || [];
so basically, get an existing array there or start one. i also do an object version of it
it's not exactly a long thing to type, but i was curious
kinda looks like a mergeRight maybe? myObject[key] = R.mergeRight(myObject[key], []);
but i'd love to just do: Init(myObject[key], []); and then its done
although i'm dumb, it'd be Init(myObject, key, []);
Ben Briggs
@coffeefedora I'd probably look at doing this when you want to extract the value out, then you can do propOr. e.g:
const results = R.propOr([], key, myObject);
In FP land we don't want to mutate our original object, so I think an Init function that has that interface would not be a good practice
yeah that kind of makes sense. i set it the way i do to make looping easier when i am adding to the array
maybe i can re-organize my code and make it a little bit differently
Ben Briggs
Yup :smile:
Hyunseok Oh
    R.zip(['x', 'y', 'z']),
    R.props(['a', 'b', 'c']),
any equivalent function?
@algoshipda That looks good to me, it seems to me there wouldn't be any much easier ways to specify a mapping like that. Are you looking for something that exhibits the same behavior in a different way?
Hyunseok Oh
@Twizzes Can't with just one ramda function?
Ben Briggs
@algoshipda 4 -> 3 with R.o(R.zipObj(['x', 'y', 'z']), R.props(['a', 'b', 'c']))
Oscar Bolmsten
Is there a "preferred" style for pipe/compose when auto formatting? Any maintainer who would care to chime in? prettier/prettier#6921
sorry if sanctuary is verbotten
Charles Hughes
anyone know a nice way to update all the keys in a given object? I need to prefix them all with a static string.. Object.entries and then R.zip comes to mind but I wish there was a cleaner way...
Brad Compton (he/him)
Something like this?
Charles Hughes
oh hell yall are already talking about this sorry for not reading :laughing:
Brad Compton (he/him)
Oh no prob! The wiki isn't well publicized
I try to bring it up whenever I can :smile:
Charles Hughes
@Twizzes do you strongly prefer Sanctuary to Ramda? I'm curious about it
Also I just wanna do a shout out. I've been using Ramda for a few months now and it is just glorious. Thanks to the developers/maintainers so much :pray:
@chughes87 the sanctuary docs do a much better job at explaining the differences than I ever could:
For a direct function to function comparison, see: https://github.com/sanctuary-js/sanctuary/wiki/Ramda-to-Sanctuary
As you can see, sanctuary is more focused, and embraces further some of the concepts of functional programming, whereas ramda has a lot more utility functions and relaxes some of the constraints traditional FP enforces, making ramda somewhat more user friendly to folks from imperitive backgrounds
Ramda is an easier sell to established teams using OOP, sanctuary is more for getting as close to FP in JavaScript as possible and a great way to learn FP for js devs
Patrick Laplante
Hello all, really dumb question. How would you handle something like a socket in a composition chain. For instance, how would I do something like this but using functional composition.
Url = “localhost:8080”
connection = open_connection(url)
result = Send_data(connection, data)
raw_response = Get_response(connection)
response = parse(response)
While I am not sure but it seems that get response should be receiving the result, if not you can curry it in but it could look like the following
        const sendData = R.curry(send_data)(R.__,data)
        const result = R.pipe(
            , sendData
            , get_response
sorry I missed some of the cases, get_response refers to Get_response and send_data refers to Send_data
if you wish to actually use compose, change pipe to compose and reverse the argument function order
Charles Hughes
I'm curious how people here generally approach debugging their Ramda code? I've found the easiest/most fluid way to be putting a breakpoint at the top of a pipe call and playing around with the code in the debug console in vscode. I've wondered if I should try Emacs since it seems to support more repl based development that I'm trying to replicate here...
I've been wondering how feasible it might be to write a little VSCode extension that would put the outputs of each line inline in faded text when you're on a breakpoint. It seems to me like it would be pretty difficult
Kurt Milam

@chughes87 I sometimes use something like this:

const log = x => (console.log(x), x)

const pipeLog = (...fns) =>
  pipe(log, ...intersperse(log, fns), log)

pipeLog(inc, inc, inc)(0) // logs 0, 1, 2, 3

// also

pipe(dec, dec, log, dec)(100) // logs 98

REPL: https://bit.ly/2QKz2P1

Matt McKellar-Spence
tap(console.log) is pretty easy for quick debugging.
var b = pipe(add(1), tap(console.log), add(1));
b(1); // = 3 (and prints 2)
Charles Hughes
Ooo the pipeLog implementation there is pretty cool thanks!
Dimitri Mitropoulos
I have a version of this I use too
const DEBUG_MODE = true;
let debugTimestamps: { [label: string]: number }[] = [];
const debugPipe = (label: string) => <T>(input: T) => {
  if (DEBUG_MODE) {
    debugTimestamps = [
        [label]: performance.now(),
    console.log({ [label]: input });
  return input;
it's basically the same thing, but allows for some recording of timestamps, and then I have a startDebug or endDebug that basically just grabs the debugTimestamps and prints the performance numbers
Hyunseok Oh
how can i make this function in ramda way?
const fn = x => id => R.prop(id, x);
Ian Hofmann-Hicks
Try R.flip(R.prop), that should flip the arguments to R.prop
The C combinator I believe it is called