define(['../internal/createAggregator'], function(createAggregator) {

/**

* 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 the last element responsible for generating the key. The

* iteratee function 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

*

* var keyData = [

* { 'dir': 'left', 'code': 97 },

* { 'dir': 'right', 'code': 100 }

* ];

*

* _.indexBy(keyData, 'dir');

* // => { 'left': { 'dir': 'left', 'code': 97 }, 'right': { 'dir': 'right', 'code': 100 } }

*

* _.indexBy(keyData, function(object) { return String.fromCharCode(object.code); });

* // => { 'a': { 'dir': 'left', 'code': 97 }, 'd': { 'dir': 'right', 'code': 100 } }

*

* _.indexBy(keyData, function(object) { return this.fromCharCode(object.code); }, String);

* // => { 'a': { 'dir': 'left', 'code': 97 }, 'd': { 'dir': 'right', 'code': 100 } }

*/

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

result[key] = value;

});

return indexBy;

});