lodash/internal/arraySum.js

define([], function() {

  /**
   * A specialized version of `_.sum` for arrays without support for callback
   * shorthands and `this` binding..
   *
   * @private
   * @param {Array} array The array to iterate over.
   * @param {Function} iteratee The function invoked per iteration.
   * @returns {number} Returns the sum.
   */
  function arraySum(array, iteratee) {
    var length = array.length,
        result = 0;

    while (length--) {
      result += +iteratee(array[length]) || 0;
    }
    return result;
  }

  return arraySum;
});