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