LibJS: Implement Intl.Locale.prototype.language

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

@@ -53,6 +53,7 @@ void LocalePrototype::initialize(GlobalObject& global_object)
     define_native_accessor(vm.names.hourCycle, hour_cycle, {}, Attribute::Configurable);
     define_native_accessor(vm.names.numberingSystem, numbering_system, {}, Attribute::Configurable);
     define_native_accessor(vm.names.numeric, numeric, {}, Attribute::Configurable);
+    define_native_accessor(vm.names.language, language, {}, Attribute::Configurable);
 }
 
 // 14.3.5 Intl.Locale.prototype.toString ( ), https://tc39.es/ecma402/#sec-Intl.Locale.prototype.toString
@@ -123,4 +124,23 @@ JS_DEFINE_NATIVE_GETTER(LocalePrototype::numeric)
     return Value(locale_object->numeric());
 }
 
+// 14.3.13 get Intl.Locale.prototype.language, https://tc39.es/ecma402/#sec-Intl.Locale.prototype.language
+JS_DEFINE_NATIVE_GETTER(LocalePrototype::language)
+{
+    // 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. Return the substring of locale corresponding to the unicode_language_subtag production of the unicode_language_id.
+    return js_string(vm, *locale->language_id.language);
+}
+
 }

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

@@ -28,6 +28,7 @@ private:
     JS_DECLARE_NATIVE_GETTER(hour_cycle);
     JS_DECLARE_NATIVE_GETTER(numbering_system);
     JS_DECLARE_NATIVE_GETTER(numeric);
+    JS_DECLARE_NATIVE_GETTER(language);
 };
 
 }

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

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