countAs - nodef/extra-map GitHub Wiki

Count occurrences of values.

Alternatives: count, countAs.

function countAs(x, fm)
// x:  a map
// fm: map function (v, k, x)

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

var x = new Map(['a', 1], ['b', 1], ['c', 2], ['d', 2], ['e', 4](/nodef/extra-map/wiki/'a',-1],-['b',-1],-['c',-2],-['d',-2],-['e',-4));
map.countAs(x);
// → Map(3) { 1 => 2, 2 => 2, 4 => 1 }

var x = new Map(['a', 1], ['b', 2], ['c', 3], ['d', 4](/nodef/extra-map/wiki/'a',-1],-['b',-2],-['c',-3],-['d',-4));
map.countAs(x, v => v % 2);
// → Map(2) { 1 => 2, 0 => 2 }

References