Fixed reduceWith and reduceRightWith not using the initial value …

…when `reduce` was called with more than three arguments

src/array/__tests__/reduceRight.spec.js

@@ -1,4 +1,5 @@
 import identity from "../../core/identity";
+import mapValuesWith from "../../object/mapValuesWith";
 import reduceRight from "../reduceRight";
 import reduceRightWith from "../reduceRightWith";
 import subtract from "../../math/subtract";
@@ -63,6 +64,13 @@ describe("reduceRight / reduceRightWith", () => {
         expect(sumMock).toHaveBeenCalledTimes(6);
     });
 
+    it("should use all the necessary arguments even if reduce is called with more than three arguements", () => {
+        // causes reduce to be called with five arguments
+        const f = mapValuesWith(reduceRightWith(sum, 7));
+
+        expect(f({ a: [...arr] }).a).toBe(22);
+    });
+
     it("should build a function throwing an exception if the accumulator isn't a function or is missing", () => {
         nonFunctions.forEach(value => {
             expect(() => { reduceRight(arr, value, 0); }).toThrow();

src/core/__tests__/reduce.spec.js

@@ -1,4 +1,5 @@
 import identity from "../identity";
+import mapValuesWith from "../../object/mapValuesWith";
 import reduce from "../reduce";
 import reduceWith from "../reduceWith";
 import subtract from "../../math/subtract";
@@ -63,6 +64,13 @@ describe("reduce / reduceWith", () => {
         expect(sumMock).toHaveBeenCalledTimes(6);
     });
 
+    it("should use all the necessary arguments even if reduce is called with more than three arguements", () => {
+        // causes reduce to be called with five arguments
+        const f = mapValuesWith(reduceWith(sum, 7));
+
+        expect(f({ a: [...arr] }).a).toBe(22);
+    });
+
     it("should build a function throwing an exception if the accumulator isn't a function or is missing", () => {
         nonFunctions.forEach(value => {
             expect(() => { reduce(arr, value, 0); }).toThrow();

src/privates/_makeReducer.js

@@ -15,17 +15,17 @@ function _makeReducer (step) {
         var nCalls;
         var result;
 
-        if (arguments.length === 3) {
-            nCalls = len;
-            result = initialValue;
-        } else {
+        if (arguments.length < 3) {
             if (len === 0) {
                 throw new TypeError("Reduce of empty array-like with no initial value");
             }
 
             result = arrayLike[idx];
             idx += step;
             nCalls = len - 1;
+        } else {
+            nCalls = len;
+            result = initialValue;
         }
 
         for (; nCalls--; idx += step) {