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