fix: date sorting doesn't work if one of the value is null

src/lib/plugins/addSortBy.test.ts

@@ -5,7 +5,7 @@ import { addSortBy } from './addSortBy';
 const data = readable([
 	{ id: 1, createdAt: new Date(2023, 1, 1), name: { first: 'Ariana', last: 'Grande' } },
 	{ id: 2, createdAt: new Date(1990, 1, 1), name: { first: 'Harry', last: 'Styles' } },
-	{ id: 3, createdAt: new Date(2025, 1, 1), name: { first: 'Doja', last: 'Cat' } },
+	{ id: 3, createdAt: null, name: { first: 'Doja', last: 'Cat' } },
 	{ id: 4, createdAt: new Date(2010, 1, 1), name: { first: 'Sam', last: 'Smith' } },
 ]);
 
@@ -45,7 +45,7 @@ test('ascending date sort', () => {
 	const vm = table.createViewModel(columns);
 	const rows = get(vm.rows);
 	const rowIds = rows.map((it) => it.isData() && it.original.id);
-	expect(rowIds).toStrictEqual([2, 4, 1, 3]);
+	expect(rowIds).toStrictEqual([3, 2, 4, 1]);
 });
 
 test('descending date sort', () => {
@@ -61,5 +61,5 @@ test('descending date sort', () => {
 	const vm = table.createViewModel(columns);
 	const rows = get(vm.rows);
 	const rowIds = rows.map((it) => it.isData() && it.original.id);
-	expect(rowIds).toStrictEqual([3, 1, 4, 2]);
+	expect(rowIds).toStrictEqual([1, 4, 2, 3]);
 });

src/lib/plugins/addSortBy.ts

@@ -138,8 +138,10 @@ const getSortedRows = <Item, Row extends BodyRow<Item>>(
 			} else if (typeof valueA === 'string' || typeof valueA === 'number') {
 				// typeof `cellB.value` is logically equal to `cellA.value`.
 				order = compare(valueA, valueB as string | number);
-			} else if (valueA instanceof Date && valueB instanceof Date) {
-				order = compare(valueA.getTime(), valueB.getTime());
+			} else if (valueA instanceof Date || valueB instanceof Date) {
+				const sortValueA = valueA instanceof Date ? valueA.getTime() : 0
+				const sortValueB = valueB instanceof Date ? valueB.getTime() : 0
+				order = compare(sortValueA, sortValueB);
 			}
 			if (order !== 0) {
 				let orderFactor = 1;