1var baseAssignValue = require('./_baseAssignValue'),
2    createAggregator = require('./_createAggregator');
3
4/** Used for built-in method references. */
5var objectProto = Object.prototype;
6
7/** Used to check objects for own properties. */
8var hasOwnProperty = objectProto.hasOwnProperty;
9
10/**
11 * Creates an object composed of keys generated from the results of running
12 * each element of `collection` thru `iteratee`. The corresponding value of
13 * each key is the number of times the key was returned by `iteratee`. The
14 * iteratee is invoked with one argument: (value).
15 *
16 * @static
17 * @memberOf _
18 * @since 0.5.0
19 * @category Collection
20 * @param {Array|Object} collection The collection to iterate over.
21 * @param {Function} [iteratee=_.identity] The iteratee to transform keys.
22 * @returns {Object} Returns the composed aggregate object.
23 * @example
24 *
25 * _.countBy([6.1, 4.2, 6.3], Math.floor);
26 * // => { '4': 1, '6': 2 }
27 *
28 * // The `_.property` iteratee shorthand.
29 * _.countBy(['one', 'two', 'three'], 'length');
30 * // => { '3': 2, '5': 1 }
31 */
32var countBy = createAggregator(function(result, value, key) {
33  if (hasOwnProperty.call(result, key)) {
34    ++result[key];
35  } else {
36    baseAssignValue(result, key, 1);
37  }
38});
39
40module.exports = countBy;
41