How to count occurrences of a path in an array of objects with ramda.js?

I'm trying to use ramda.js to count occurrences of a key-value pair inside an array of objects, such as:

ramda.js

var array = [
{a: {b: 'a'}},
{a: {b: 'a'}},
{a: {b: 'X'}},
{a: 'a'}
]


If I wanted to count the number of times {a: {b: 'a'}} occurs inside of array in ramda.js, what would I do?

{a: {b: 'a'}}

array

ramda.js

R.pathEq

R.map

true

false

Number

true

1

false

0

R.sum

1

1 Answer
1

You may hate it, pointfree function.

R.compose(R.length, R.filter(R.compose( R.equals('a'), R.path(['a', 'b']))))(array)


UPDATE Just learned from comment of Scott Christopher.

R.compose(R.equals(val), R.Path(p1, p2)) == R.pathEq([p1, p2], val)

function can be shorten to

R.compose(R.length, R.filter(R.pathEq(['a', 'b'], 'a')))(array)


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