fix: nested parent ids did not work if parent was null or undefined

Author: philipstanislaus

src/arrayToTree.spec.ts

@@ -495,6 +495,7 @@ describe("arrayToTree", () => {
       },
     ]);
   });
+
   it("should work with nested id property", () => {
     expect(
       arrayToTree(
@@ -516,6 +517,7 @@ describe("arrayToTree", () => {
       },
     ]);
   });
+
   it("should work with nested parentId property", () => {
     expect(
       arrayToTree(
@@ -537,6 +539,7 @@ describe("arrayToTree", () => {
       },
     ]);
   });
+
   it("should work with nested id and parentId properties", () => {
     expect(
       arrayToTree(
@@ -558,4 +561,48 @@ describe("arrayToTree", () => {
       },
     ]);
   });
+
+  it("should work with nested id and parentId properties if the parent is null", () => {
+    expect(
+      arrayToTree(
+        [
+          { one: { id: "1" }, two: null, custom: "1" },
+          { one: { id: "1.1" }, two: { parentId: "1" }, custom: "1.1" },
+        ],
+        { id: "one.id", parentId: "two.parentId" }
+      )
+    ).to.deep.equal([
+      {
+        data: { one: { id: "1" }, two: null, custom: "1" },
+        children: [
+          {
+            data: { one: { id: "1.1" }, two: { parentId: "1" }, custom: "1.1" },
+            children: [],
+          },
+        ],
+      },
+    ]);
+  });
+
+  it("should work with nested id and parentId properties if the parent is undefined", () => {
+    expect(
+      arrayToTree(
+        [
+          { one: { id: "1" }, custom: "1" },
+          { one: { id: "1.1" }, two: { parentId: "1" }, custom: "1.1" },
+        ],
+        { id: "one.id", parentId: "two.parentId" }
+      )
+    ).to.deep.equal([
+      {
+        data: { one: { id: "1" }, custom: "1" },
+        children: [
+          {
+            data: { one: { id: "1.1" }, two: { parentId: "1" }, custom: "1.1" },
+            children: [],
+          },
+        ],
+      },
+    ]);
+  });
 });

src/arrayToTree.ts

@@ -140,5 +140,5 @@ export function arrayToTree(
  * @param nestedProperty the chained properties to access the nested property. Eg: 'your.nested.property'
  */
 function getNestedProperty(item: Item, nestedProperty: string) {
-  return nestedProperty.split(".").reduce((o, i) => o[i], item);
+  return nestedProperty.split(".").reduce((o, i) => o && o[i], item);
 }