added unit testing, and started implementing unit tests...phew

node_modules/lodash/zipWith.js

@@ -0,0 +1,32 @@
+var baseRest = require('./_baseRest'),
+    unzipWith = require('./unzipWith');
+
+/**
+ * This method is like `_.zip` except that it accepts `iteratee` to specify
+ * how grouped values should be combined. The iteratee is invoked with the
+ * elements of each group: (...group).
+ *
+ * @static
+ * @memberOf _
+ * @since 3.8.0
+ * @category Array
+ * @param {...Array} [arrays] The arrays to process.
+ * @param {Function} [iteratee=_.identity] The function to combine
+ *  grouped values.
+ * @returns {Array} Returns the new array of grouped elements.
+ * @example
+ *
+ * _.zipWith([1, 2], [10, 20], [100, 200], function(a, b, c) {
+ *   return a + b + c;
+ * });
+ * // => [111, 222]
+ */
+var zipWith = baseRest(function(arrays) {
+  var length = arrays.length,
+      iteratee = length > 1 ? arrays[length - 1] : undefined;
+
+  iteratee = typeof iteratee == 'function' ? (arrays.pop(), iteratee) : undefined;
+  return unzipWith(arrays, iteratee);
+});
+
+module.exports = zipWith;