1var baseIteratee = require('./_baseIteratee'),
2    baseSum = require('./_baseSum');
3
4/**
5 * This method is like `_.sum` except that it accepts `iteratee` which is
6 * invoked for each element in `array` to generate the value to be summed.
7 * The iteratee is invoked with one argument: (value).
8 *
9 * @static
10 * @memberOf _
11 * @since 4.0.0
12 * @category Math
13 * @param {Array} array The array to iterate over.
14 * @param {Function} [iteratee=_.identity] The iteratee invoked per element.
15 * @returns {number} Returns the sum.
16 * @example
17 *
18 * var objects = [{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }];
19 *
20 * _.sumBy(objects, function(o) { return o.n; });
21 * // => 20
22 *
23 * // The `_.property` iteratee shorthand.
24 * _.sumBy(objects, 'n');
25 * // => 20
26 */
27function sumBy(array, iteratee) {
28  return (array && array.length)
29    ? baseSum(array, baseIteratee(iteratee, 2))
30    : 0;
31}
32
33module.exports = sumBy;
34