Counts occurrences of values. :running: :vhs: :package: :moon:

Alternatives: one, all. This is part of package extra-array.

This is browserified, minified version of @extra-array/count-on. It is exported as global variable array_countOn. CDN: unpkg, jsDelivr.

array.countOn(x, [fn], [ths]);
// x:   an array
// fn:  map function (v, i, x)
// ths: this argument
// --> Map {value => count}

const array = require('extra-array');

var x = [1, 1, 2, 2, 4];
array.countOn(x);
// Map(3) { 1 => 2, 2 => 2, 4 => 1 }

var x = [1, 2, 3, 4];
array.countOn(x, v => v % 2);
// Map(2) { 1 => 2, 0 => 2 }

references

• count-array-values: @zeke
• _.countBy(): lodash
• List-Extra.count(): elm