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- var baseAssignValue = require('./_baseAssignValue'),
- createAggregator = require('./_createAggregator');
- /** Used for built-in method references. */
- var objectProto = Object.prototype;
- /** Used to check objects for own properties. */
- var hasOwnProperty = objectProto.hasOwnProperty;
- /**
- * Creates an object composed of keys generated from the results of running
- * each element of `collection` thru `iteratee`. The corresponding value of
- * each key is the number of times the key was returned by `iteratee`. The
- * iteratee is invoked with one argument: (value).
- *
- * @static
- * @memberOf _
- * @since 0.5.0
- * @category Collection
- * @param {Array|Object} collection The collection to iterate over.
- * @param {Function} [iteratee=_.identity] The iteratee to transform keys.
- * @returns {Object} Returns the composed aggregate object.
- * @example
- *
- * _.countBy([6.1, 4.2, 6.3], Math.floor);
- * // => { '4': 1, '6': 2 }
- *
- * // The `_.property` iteratee shorthand.
- * _.countBy(['one', 'two', 'three'], 'length');
- * // => { '3': 2, '5': 1 }
- */
- var countBy = createAggregator(function(result, value, key) {
- if (hasOwnProperty.call(result, key)) {
- ++result[key];
- } else {
- baseAssignValue(result, key, 1);
- }
- });
- module.exports = countBy;
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