feat(extract): add unwrapOr operator

operators/extract.ts

@@ -30,6 +30,24 @@ export function unwrap<T>(option: Option<T>): T {
   throw new Error("option is None");
 }
 
+/** Returns the contained `Some` value, otherwise {@link defaultValue}.
+ *
+ * @example
+ * ```ts
+ * import { None, Some } from "https://deno.land/x/optio/spec.ts";
+ * import { unwrapOr } from "https://deno.land/x/optio/mod.ts";
+ * import { assertEquals } from "https://deno.land/std/testing/asserts.ts";
+ *
+ * assertEquals(unwrapOr(Some.of(0), 1), 0);
+ * assertEquals(unwrapOr(None, 1), 1);
+ * ```
+ */
+export function unwrapOr<T>(option: Option<T>, defaultValue: T): T {
+  if (isSome(option)) return option.get;
+
+  return defaultValue;
+}
+
 /** Returns the contained `Some` value.
  *
  * @example

operators/extract_test.ts

@@ -1,7 +1,7 @@
 // Copyright © 2023 Tomoki Miyauchi. All rights reserved. MIT license.
 // This module is browser compatible.
 
-import { expect, unwrap } from "./extract.ts";
+import { expect, unwrap, unwrapOr } from "./extract.ts";
 import { None, Some } from "../spec.ts";
 import { assertEquals, assertThrows, describe, it } from "../_dev_deps.ts";
 
@@ -15,6 +15,16 @@ describe("unwrap", () => {
   });
 });
 
+describe("unwrapOr", () => {
+  it("should some value if some", () => {
+    assertEquals(unwrapOr(Some.of(0), 1), 0);
+  });
+
+  it("should default value if None", () => {
+    assertEquals(unwrapOr(None, 1), 1);
+  });
+});
+
 describe("expect", () => {
   it("should return some value", () => {
     assertEquals(expect(Some.of(0), ""), 0);