Function createAggregator

lib/web/jshint.js:4550–4570

* Creates a function that aggregates a collection, creating an accumulator * object composed from the results of running each element in the collection * through an iteratee. * * **Note:** This function is used to create `_.countBy`, `_.groupBy`, `_.indexBy`, * and `_.partit

(setter, initializer)

     * @returns {Function} Returns the new aggregator function.
     */
    function createAggregator(setter, initializer) {
      return function(collection, iteratee, thisArg) {
        var result = initializer ? initializer() : {};
        iteratee = getCallback(iteratee, thisArg, 3);

        if (isArray(collection)) {
          var index = -1,
              length = collection.length;

          while (++index < length) {
            var value = collection[index];
            setter(result, value, iteratee(value, index, collection), collection);
          }
        } else {
          baseEach(collection, function(value, key, collection) {
            setter(result, value, iteratee(value, key, collection), collection);
          });
        }
        return result;
      };
    }

    /**
     * Creates a function that assigns properties of source object(s) to a given