import group from './_group.js';
import has from './_has.js';
import group from './_group.js';
import has from './_has.js';
Counts instances of an object that group by a certain criterion. Pass either a string attribute to count by, or a function that returns the criterion.
export default group(function(result, value, key) {
if (has(result, key)) result[key]++; else result[key] = 1;
});