ramda/ramda

Practical functional Javascript

Ian Hofmann-Hicks

@evilsoft

I just do not use the OO bits because of my aversion to state

Brad Compton (he/him)

@Bradcomp

Most languages don't use prototypical inheritance

The scoping is weird and it didn't get classes till 2015-ish?

Long Dao

@longebane

but isn't prototypical inheritance still a subset of OO

Brad Compton (he/him)

@Bradcomp

Then you have stuff like calland apply

It is, but if it was inspired by Java it certainly had a ... unique take

Ian Hofmann-Hicks

@evilsoft

Yes, but not the norm @longebane. what some would call Traditional OO

Brad Compton (he/him)

@Bradcomp

You can use prototypes similar to classes, but they can also be used for some rad metaprogramming, multiple inheritance, mixins, etc.

Long Dao

@longebane

Ok, then instead of "JS is an OO language", what would be better?

that's essentially what I'm getting at

Brad Compton (he/him)

@Bradcomp

JS is a multi-paradigm language supporting OO, Functional, and Imperative programming styles, as well as allowing the user to mix and match

Long Dao

@longebane

deja vu. I feel like I've seen that before

Ian Hofmann-Hicks

@evilsoft

:+1: to that @Bradcomp

Long Dao

@longebane

looks great!

Ian Hofmann-Hicks

@evilsoft

:sheep: :it:

Long Dao

@longebane

:red_circle: :eyes:

Brad Compton (he/him)

@Bradcomp

Because of this, it can support a wide variety of applications and use cases. It also provides a number of footguns for users that await the incautious developer.

Long Dao

@longebane

footgun?

Brad Compton (he/him)

@Bradcomp

It will pretty much let you do anything and won't try to stop you

Long Dao

@longebane

traps?

Brad Compton (he/him)

@Bradcomp

Leading to a number of ways to shoot yourself in the foot

self sabotage

:stuck_out_tongue_closed_eyes:

Long Dao

@longebane

yeah. good stuff. thanks my brah's

Ian Hofmann-Hicks

@evilsoft

Anytime! Is your course going to be public?

Carl Parrish

@carl-parrish

I have an object {} my object may have several nested properties.
const myObj = {prop1: {prop2: {prop3: data: null}}}
I need to set data if it's empty

 if ( R.isNil(myObj.prop1.prop2.prop3.data))
  {
     myObj.prop1.prop2.prop3.data = myCurrentDataObj ;
 }

This works as long a prop1, prop2 & prop3 exists. But sometimes they don't so I tried

If (R.isNil(myObj.prop1)){ myObj.pro1 = {prop2: {prop3: data: {}}}; }

Do I actually have to explicitly check to see if every property has been defined before I can set data? I was hoping that something like R.lensProp and R.set could solve this for me but if so I haven't figured it out yet.

Brad Compton (he/him)

@Bradcomp

Look at R.pathSatisfies

and other similar functions

Carl Parrish

@carl-parrish

thanks

Brad Compton (he/him)

@Bradcomp

const dataPath =  ['prop1', 'prop2', 'prop3', 'data'];
when (
  pathSatisfies(isNil, dataPath),
  assocPath(dataPath, {})
)(myObj);

assocPath will create intermediate properties I am pretty sure

Carl Parrish

@carl-parrish

will try that now.

Brad Compton (he/him)

@Bradcomp

also change out the {} with myCurrentDataObj

and it won't update your input, but instead create a new object based on the old one

Carl Parrish

@carl-parrish

but only if it was nil right?

Brad Compton (he/him)

@Bradcomp

If pathSatisfies returns false (the property isn't nil) then it will just return myObj unchanged

dimatter

@dimatter

hey all. what is wrong with the following? const previous = R.defaultTo([0,0], R.nth(-1))

when calling it with an empty array I was expecting the defaults

Riku Tiira

@rikutiira

@dimatter you are checking default of a truthly value (a curried function returned R.nth(-1))

You could do R.compose(R.defaultTo([0,0]), R.nth(-1))

Ben Briggs

@ben-eb

Ooo, I hadn't used sortWith before, that's better still :)

pentatronix

@pentatronix

How would one traverse with a lensPath? I have been trying to wrap my brain around partial.lenses for a while and I get nowhere :(
What I would be after is the equivalent to x = lensPath(['a', *, 'd']); which would return all d children of any elements that are children of a.

Twizzes

@Twizzes

const obj = { a: [{ d: 1 }, { d: 2 }, { d: 3 }] };
const aChildrenD = R.pipe(R.view(R.lensProp("a")), R.map(R.view(R.lensProp("d"))));

console.log(aChildrenD(obj));
// => [1,2,3]

this only works if a can be operated on by R.map

@pentatronix

pentatronix

@pentatronix

@Twizzes , ah makes sense. So effectively you build up lenses of the sub objects, and wherever you need to you just compose with map or reduce etc.

pentatronix

@pentatronix

Thanks. I had not seen a particularly clear usage for lenses, especially in complex read only situations.

Alex McKay

@alexandermckay

I am trying to a find a function in the ramda library that does the same thing as the callback helper function I have written below. Could someone please let me know if it exists?

const callback = (fn) => (...args) => () => fn(...args)

const obj = {
  method: (x, y) => x + y
}

const exists = always(has('method', obj))
const execute = callback(prop('method', obj))('Invoke ', 'Fn')

when(exists, execute)(null)

Brad Compton (he/him)

@Bradcomp

https://ramdajs.com/docs/#thunkify

@alexandermckay That might be what you are looking for.

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