Ramda - filtering array of objects - curried fn parameters order

Question

I want to implement filtering function generator in ramda.js. In my mind, it should works this way:

var a = filterFn(arrOfObjects)
var b = a(keyName)
var c = b(value)

It's very imporant to achieve this order of arguments, because the same array could be filtered using different conditions.

Currently I have the following code:

var g = R.curryN(2, R.compose(R.filter(R.__)(R.__), R.propEq))
g('classId')(2)(input)

but I want to have 'input' as first argument:

g(input)('classId')(1)

Here is a ramda REPL: code

Thanks in advance!

Answer 1

I would just use something like this:

R.curry((list, name, value) => R.filter(R.propEq(name, value), list));

Ramda does not include an arbitrary parameter-reordering mechanism, just flip and the __ placeholder .

Answer 2

You don't really want this function to be pointfree :)

var g = R.compose(
  R.curryN(2, R.compose)(R.__, R.propEq),
  R.curryN(2, R.compose),
  R.flip(R.filter)
)

Or atleast make sure future maintainer would never know where you live :)

How to get something terrible like this one.

First, you write pointful version of your function which is straight forward.

list => prop => value => R.filter(R.propEq(prop)(value))(list)

or

list => prop => value = R.flip(R.filter)(list)(R.propEq(prop)(value))

Then go to Pointfree.io and use some haskell syntax \\xyz -> fx (gyz) . Where f if flip filter and g is propEq

Tool would produce (. g) . (.) . f (. g) . (.) . f

Then you convert this back to javascript to make future maintainer cry. Demo .