1
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var baseAssignValue = require('./_baseAssignValue'),
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2
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createAggregator = require('./_createAggregator');
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3
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4
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/** Used for built-in method references. */
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5
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var objectProto = Object.prototype;
|
6
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|
7
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/** Used to check objects for own properties. */
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8
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var hasOwnProperty = objectProto.hasOwnProperty;
|
9
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|
10
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/**
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11
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* Creates an object composed of keys generated from the results of running
|
12
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* each element of `collection` thru `iteratee`. The corresponding value of
|
13
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* each key is the number of times the key was returned by `iteratee`. The
|
14
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* iteratee is invoked with one argument: (value).
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15
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*
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16
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* @static
|
17
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* @memberOf _
|
18
|
* @since 0.5.0
|
19
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* @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
|
*/
|
32
|
var 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
|
|
40
|
module.exports = countBy;
|