import createAggregator from '../internal/createAggregator';

/** Used for native 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` through `iteratee`. The corresponding value

* of each key is an array of the elements responsible for generating the key.

* The `iteratee` is bound to `thisArg` and invoked with three arguments;

* (value, index|key, collection).

*

* If a property name is provided for `predicate` the created "_.property"

* style callback returns the property value of the given element.

*

* If an object is provided for `predicate` the created "_.matches" style

* callback returns `true` for elements that have the properties of the given

* object, else `false`.

*

* @static

* @memberOf _

* @category Collection

* @param {Array|Object|string} collection The collection to iterate over.

* @param {Function|Object|string} [iteratee=_.identity] The function invoked

* per iteration. If a property name or object is provided it is used to

* create a "_.property" or "_.matches" style callback respectively.

* @param {*} [thisArg] The `this` binding of `iteratee`.

* @returns {Object} Returns the composed aggregate object.

* @example

*

* _.groupBy([4.2, 6.1, 6.4], function(n) { return Math.floor(n); });

* // => { '4': [4.2], '6': [6.1, 6.4] }

*

* _.groupBy([4.2, 6.1, 6.4], function(n) { return this.floor(n); }, Math);

* // => { '4': [4.2], '6': [6.1, 6.4] }

*

* // using the "_.property" callback shorthand

* _.groupBy(['one', 'two', 'three'], 'length');

* // => { '3': ['one', 'two'], '5': ['three'] }

*/

var groupBy = createAggregator(function(result, value, key) {

if (hasOwnProperty.call(result, key)) {

result[key].push(value);

} else {

result[key] = [value];

}

});

export default groupBy;