fix(observable-array): reduce no longer ignores zero as initial value (NativeScript#6402)

surdu · Alexander Vakrilov · commit c0438df9a7c5 · 2018-10-19T17:14:47.000+03:00
* fix(observable-array): reduce no longer ignores zero as initial value

* fix(observable-array): reduceRight now functions  properly when initial value is not specified or zero
diff --git a/tests/app/data/observable-array-tests.ts b/tests/app/data/observable-array-tests.ts
@@ -646,6 +646,34 @@ export const test_reduce_with_initial_value = function () {
     TKUnit.assertEqual(result, 11, "ObservableArray reduce function broken when Initial Value is passed.");
 };
 
+export const test_reduce_with_zero_as_initial_value = function () {
+    const sa = [{prop: 1}, {prop: 2}, {prop: 3}];
+    let array: ObservableArray<any> = new ObservableArray(sa);
+    const result = array.reduce((a, b) => a + b.prop, 0);
+    TKUnit.assertEqual(result, 6, "ObservableArray reduce function broken when Initial Value is zero.");
+};
+
 export const test_reduceRight_isDefined = function () {
     TKUnit.assert(typeof (array.reduceRight) === "function", "Method 'reduceRight()' should be defined!");
 };
+
+export const test_reduceRight_without_initial_value = function () {
+    const sa = [1, 2, 3];
+    let array: ObservableArray<number> = new ObservableArray(sa);
+    const result = array.reduceRight((a, b) => a + b);
+    TKUnit.assertEqual(result, 6, "ObservableArray reduceRight function broken when initialValue is missing");
+};
+
+export const test_reduceRight_with_initial_value = function () {
+    const sa = [1, 2, 3];
+    let array: ObservableArray<number> = new ObservableArray(sa);
+    const result = array.reduceRight((a, b) => a + b, 5);
+    TKUnit.assertEqual(result, 11, "ObservableArray reduceRight function broken when Initial Value is passed.");
+};
+
+export const test_reduceRight_with_zero_as_initial_value = function () {
+    const sa = [{prop: 1}, {prop: 2}, {prop: 3}];
+    let array: ObservableArray<any> = new ObservableArray(sa);
+    const result = array.reduceRight((a, b) => a + b.prop, 0);
+    TKUnit.assertEqual(result, 6, "ObservableArray reduceRight function broken when Initial Value is zero.");
+};
diff --git a/tns-core-modules/data/observable-array/observable-array.ts b/tns-core-modules/data/observable-array/observable-array.ts
@@ -1,4 +1,4 @@
-﻿import * as observable from "../observable";
+import * as observable from "../observable";
 import * as observableArrayDef from ".";
 import * as types from "../../utils/types";
 
@@ -314,7 +314,7 @@ export class ObservableArray<T> extends observable.Observable implements observa
      * @param initialValue If initialValue is specified, it is used as the initial value to start the accumulation. The first call to the callbackfn function provides this value as an argument instead of an array value.
      */
     reduce(callbackfn: (previousValue: T, currentValue: T, currentIndex: number, array: T[]) => T, initialValue?: T): T {
-        return initialValue ? this._array.reduce(callbackfn, initialValue) : this._array.reduce(callbackfn);
+        return initialValue !== undefined ? this._array.reduce(callbackfn, initialValue) : this._array.reduce(callbackfn);
     }
 
     /**
@@ -323,12 +323,12 @@ export class ObservableArray<T> extends observable.Observable implements observa
      * @param initialValue If initialValue is specified, it is used as the initial value to start the accumulation. The first call to the callbackfn function provides this value as an argument instead of an array value.
      */
     reduceRight(callbackfn: (previousValue: T, currentValue: T, currentIndex: number, array: T[]) => T, initialValue?: T): T {
-        return this._array.reduceRight(callbackfn, initialValue);
+        return initialValue !== undefined ? this._array.reduceRight(callbackfn, initialValue) : this._array.reduceRight(callbackfn);
     }
 }
 
 export interface ObservableArray<T> {
     on(eventNames: string, callback: (data: observable.EventData) => void, thisArg?: any);
 
     on(event: "change", callback: (args: observableArrayDef.ChangedData<T>) => void, thisArg?: any);
-}
+}
