feat: add date comparison utils

src/shared/utils/date.test.ts

@@ -0,0 +1,26 @@
+import assert from "node:assert/strict"
+import { describe, it } from "node:test"
+import { compareDate } from "./date.ts"
+
+describe("compareDate", () => {
+  it("returns a negative value if the first date is earlier than the second date", () => {
+    assert.equal(
+      compareDate(new Date(2000, 0, 1, 12, 0, 0, 100), new Date(2000, 0, 1, 12, 0, 0, 200)),
+      -100,
+    )
+  })
+
+  it("returns a positive value if the first date is later than the second date", () => {
+    assert.equal(
+      compareDate(new Date(2000, 0, 1, 12, 0, 0, 300), new Date(2000, 0, 1, 12, 0, 0, 200)),
+      100,
+    )
+  })
+
+  it("returns zero if the first date is equal to the second date", () => {
+    assert.equal(
+      compareDate(new Date(2000, 0, 1, 12, 0, 0, 200), new Date(2000, 0, 1, 12, 0, 0, 200)),
+      0,
+    )
+  })
+})

src/shared/utils/date.ts

@@ -0,0 +1,6 @@
+import { Compare } from "./compare.ts"
+
+/**
+ * A comparator function for {@link Date} objects in ascending order.
+ */
+export const compareDate: Compare<Date> = (a, b) => a.getTime() - b.getTime()