How to count occurrences of a path in an array of objects with ramda.js?
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)
Thank you, I think it's a good way as it's very concise :-) jsfiddle.net/8s9ae61L
– Gallaxhar
Jul 2 at 9:50
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Think in terms of these steps: [1]
R.pathEqto check whether an array element matches [2]R.mapto check every element of the array, converting it totrueorfalse[3]Numbercan be used as a function to convert fromtrueto1andfalseto0[4]R.sumto tally up all the1s in the array Let me know if you need more assistance than the above and I can provide a complete solution.– Scott Christopher
Jul 2 at 9:24