aaac7fed
 liuqimichale
add
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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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