HORIZON PROJECT

var baseIteratee = require('./_baseIteratee'),

    baseSum = require('./_baseSum');

/**

 * This method is like `_.sum` except that it accepts `iteratee` which is

 * invoked for each element in `array` to generate the value to be summed.

 * The iteratee is invoked with one argument: (value).

 *

 * @static

 * @memberOf _

 * @since 4.0.0

 * @category Math

 * @param {Array} array The array to iterate over.

 * @param {Function} [iteratee=_.identity] The iteratee invoked per element.

 * @returns {number} Returns the sum.

 * @example

 *

 * var objects = [{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }];

 *

 * _.sumBy(objects, function(o) { return o.n; });

 * // => 20

 *

 * // The `_.property` iteratee shorthand.

 * _.sumBy(objects, 'n');

 * // => 20

 */

function sumBy(array, iteratee) {

  return (array && array.length)

    ? baseSum(array, baseIteratee(iteratee, 2))

    : 0;

}

module.exports = sumBy;