Counts occurrences of values. :running: :vhs: :package: :moon: :ledger:
Alternatives: one, all.
This is part of package extra-iterable.
iterable.countOn(x, [fn], [ths]);
// x: an iterable
// fn: map function (v, i, x)
// ths: this argument
// --> Map {value => count}const iterable = require('extra-iterable');
var x = [1, 1, 2, 2, 4];
iterable.countOn(x);
// Map(3) { 1 => 2, 2 => 2, 4 => 1 }
var x = [1, 2, 3, 4];
iterable.countOn(x, v => v % 2);
// Map(2) { 1 => 2, 0 => 2 }