LibJS: Implement Intl.Locale.prototype.region

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

@@ -55,6 +55,7 @@ void LocalePrototype::initialize(GlobalObject& global_object)
     define_native_accessor(vm.names.numeric, numeric, {}, Attribute::Configurable);
     define_native_accessor(vm.names.language, language, {}, Attribute::Configurable);
     define_native_accessor(vm.names.script, script, {}, Attribute::Configurable);
+    define_native_accessor(vm.names.region, region, {}, Attribute::Configurable);
 }
 
 // 14.3.5 Intl.Locale.prototype.toString ( ), https://tc39.es/ecma402/#sec-Intl.Locale.prototype.toString
@@ -167,4 +168,27 @@ JS_DEFINE_NATIVE_GETTER(LocalePrototype::script)
     return js_string(vm, *locale->language_id.script);
 }
 
+// 14.3.15 get Intl.Locale.prototype.region, https://tc39.es/ecma402/#sec-Intl.Locale.prototype.region
+JS_DEFINE_NATIVE_GETTER(LocalePrototype::region)
+{
+    // 1. Let loc be the this value.
+    // 2. Perform ? RequireInternalSlot(loc, [[InitializedLocale]]).
+    auto* locale_object = typed_this(global_object);
+    if (!locale_object)
+        return {};
+
+    // 3. Let locale be loc.[[Locale]].
+    auto locale = Unicode::parse_unicode_locale_id(locale_object->locale());
+
+    // 4. Assert: locale matches the unicode_locale_id production.
+    VERIFY(locale.has_value());
+
+    // 5. If the unicode_language_id production of locale does not contain the ["-" unicode_region_subtag] sequence, return undefined.
+    if (!locale->language_id.region.has_value())
+        return js_undefined();
+
+    // 6. Return the substring of locale corresponding to the unicode_region_subtag production of the unicode_language_id.
+    return js_string(vm, *locale->language_id.region);
+}
+
 }

Userland/Libraries/LibJS/Runtime/Intl/LocalePrototype.h

@@ -30,6 +30,7 @@ private:
     JS_DECLARE_NATIVE_GETTER(numeric);
     JS_DECLARE_NATIVE_GETTER(language);
     JS_DECLARE_NATIVE_GETTER(script);
+    JS_DECLARE_NATIVE_GETTER(region);
 };
 
 }

Userland/Libraries/LibJS/Tests/builtins/Intl/Locale/Locale.prototype.region.js

@@ -0,0 +1,21 @@
+describe("errors", () => {
+    test("called on non-Locale object", () => {
+        expect(() => {
+            Intl.Locale.prototype.region;
+        }).toThrowWithMessage(TypeError, "Not a Intl.Locale object");
+    });
+});
+
+describe("normal behavior", () => {
+    test("basic functionality", () => {
+        expect(new Intl.Locale("en").region).toBeUndefined();
+        expect(new Intl.Locale("en-Latn").region).toBeUndefined();
+        expect(new Intl.Locale("en-GB").region).toBe("GB");
+        expect(new Intl.Locale("en", { script: "Latn" }).region).toBeUndefined();
+        expect(new Intl.Locale("en", { region: "GB" }).region).toBe("GB");
+
+        expect(new Intl.Locale("en-u-ca-abc").region).toBeUndefined();
+        expect(new Intl.Locale("en", { calendar: "abc" }).region).toBeUndefined();
+        expect(new Intl.Locale("en-x-abcd").region).toBeUndefined();
+    });
+});