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4 years ago
  1. 'use strict';
  2. module.exports = function countBy() {
  3. var fn = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : function (value) {
  4. return value;
  5. };
  6. return new this.constructor(this.items).groupBy(fn).map(function (value) {
  7. return value.count();
  8. });
  9. };