LibJS: Extend Intl.DisplayNames.of to support currency tags

Author: https://github.com/trflynn89
Commit: 86b99fd9a6
Pull-request: https://github.com/SerenityOS/serenity/pull/9622
Reviewed-by: https://github.com/linusg

Userland/Libraries/LibJS/Runtime/Intl/DisplayNamesPrototype.cpp

@@ -86,6 +86,7 @@ JS_DEFINE_NATIVE_FUNCTION(DisplayNamesPrototype::of)
         result = Unicode::get_locale_script_mapping(display_names->locale(), code.as_string().string());
         break;
     case DisplayNames::Type::Currency:
+        result = Unicode::get_locale_currency_mapping(display_names->locale(), code.as_string().string());
         break;
     default:
         VERIFY_NOT_REACHED();

Userland/Libraries/LibJS/Tests/builtins/Intl/DisplayNames/DisplayNames.prototype.of.js

@@ -73,4 +73,19 @@ describe("correct behavior", () => {
         expect(es419.of("Aaaa")).toBe("Aaaa");
         expect(zhHant.of("Aaaa")).toBe("Aaaa");
     });
+
+    test("option type currency", () => {
+        const en = new Intl.DisplayNames("en", { type: "currency" });
+        expect(en.of("USD")).toBe("US Dollar");
+
+        const es419 = new Intl.DisplayNames("es-419", { type: "currency" });
+        expect(es419.of("USD")).toBe("dólar estadounidense");
+
+        const zhHant = new Intl.DisplayNames(["zh-Hant"], { type: "currency" });
+        expect(zhHant.of("USD")).toBe("美元");
+
+        expect(en.of("AAA")).toBe("AAA");
+        expect(es419.of("AAA")).toBe("AAA");
+        expect(zhHant.of("AAA")).toBe("AAA");
+    });
 });