--- /dev/null
+/**
+ * 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;
+}
+
+module.exports = arraySum;