LibWeb: Implement DOMStringList

Author: https://github.com/jamierocks
Commit: 75216182c9
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/731
Reviewed-by: https://github.com/AtkinsSJ

Userland/Libraries/LibWeb/HTML/DOMStringList.cpp

@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2024, Jamie Mansfield <jmansfield@cadixdev.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/Bindings/DOMStringListPrototype.h>
+#include <LibWeb/Bindings/Intrinsics.h>
+#include <LibWeb/HTML/DOMStringList.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
+
+namespace Web::HTML {
+
+JS_DEFINE_ALLOCATOR(DOMStringList);
+
+JS::NonnullGCPtr<DOMStringList> DOMStringList::create(JS::Realm& realm, Vector<String> list)
+{
+    return realm.heap().allocate<DOMStringList>(realm, realm, list);
+}
+
+DOMStringList::DOMStringList(JS::Realm& realm, Vector<String> list)
+    : Bindings::PlatformObject(realm)
+    , m_list(move(list))
+{
+    m_legacy_platform_object_flags = LegacyPlatformObjectFlags { .supports_indexed_properties = true };
+}
+
+void DOMStringList::initialize(JS::Realm& realm)
+{
+    Base::initialize(realm);
+    WEB_SET_PROTOTYPE_FOR_INTERFACE(DOMStringList);
+}
+
+// https://html.spec.whatwg.org/multipage/common-dom-interfaces.html#dom-domstringlist-length
+u32 DOMStringList::length() const
+{
+    // The length getter steps are to return this's associated list's size.
+    return m_list.size();
+}
+
+// https://html.spec.whatwg.org/multipage/common-dom-interfaces.html#dom-domstringlist-item
+Optional<String> DOMStringList::item(u32 index) const
+{
+    // The item(index) method steps are to return the indexth item in this's associated list, or null if index plus one
+    // is greater than this's associated list's size.
+    if (index + 1 > m_list.size())
+        return {};
+
+    return m_list.at(index);
+}
+
+// https://html.spec.whatwg.org/multipage/common-dom-interfaces.html#dom-domstringlist-contains
+bool DOMStringList::contains(StringView string)
+{
+    // The contains(string) method steps are to return true if this's associated list contains string, and false otherwise.
+    return m_list.contains_slow(string);
+}
+
+bool DOMStringList::is_supported_property_index(u32 index) const
+{
+    // The DOMStringList interface supports indexed properties. The supported property indices are the indices of this's
+    // associated list.
+    return index < m_list.size();
+}
+
+WebIDL::ExceptionOr<JS::Value> DOMStringList::item_value(size_t index) const
+{
+    if (index + 1 > m_list.size())
+        return JS::js_undefined();
+
+    return JS::PrimitiveString::create(vm(), m_list.at(index));
+}
+
+}