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Code Issues Projects Releases Packages Wiki Activity Actions 11

LibWeb: Avoid copying cached elements in HTMLCollection

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Once we have built up a cache, we can use that internally for operations
on the collection, instead of copying over the list of elements every
time.

On a synthentic benchmark of a page with ~500 link elements, this
results in a 45% percent speedup on my machine.

```html
<body>
    <ul>
        <li><a href="#">Link 1</a></li>
        ...
        <li><a href="#">Link N</a></li>
    </ul>

    <script>
        window.onload = function() {
            const startTime = performance.now();
            for (let i = 0; i < 1_000_000; ++i) {
                const numLinks = document.links.length;
            }
            const endTime = performance.now();
            const timeTaken = endTime - startTime;
            console.log(timeTaken);
        };
    </script>
</body>
</html>
```
This commit is contained in:
Shannon Booth 2024-04-01 15:31:12 +02:00 • committed by Andreas Kling
parent 094ab8b4d2
commit adf061a29c
Notes: sideshowbarker 2024-07-17 06:38:11 +09:00
1 changed files with 11 additions and 8 deletions
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19
Userland/Libraries/LibWeb/DOM/HTMLCollection.cpp
View file

@ -86,17 +86,18 @@ JS::MarkedVector<JS::NonnullGCPtr<Element>> HTMLCollection::collect_matching_ele
size_t HTMLCollection::length() const
{
// The length getter steps are to return the number of nodes represented by the collection.
return collect_matching_elements().size();
update_cache_if_needed();
return m_cached_elements.size();
}
// https://dom.spec.whatwg.org/#dom-htmlcollection-item
Element* HTMLCollection::item(size_t index) const
{
// The item(index) method steps are to return the indexth element in the collection. If there is no indexth element in the collection, then the method must return null.
auto elements = collect_matching_elements();
if (index >= elements.size())
update_cache_if_needed();
if (index >= m_cached_elements.size())
return nullptr;
return elements[index];
return m_cached_elements[index];
}
// https://dom.spec.whatwg.org/#dom-htmlcollection-nameditem-key
@ -105,7 +106,10 @@ Element* HTMLCollection::named_item(FlyString const& name) const
// 1. If key is the empty string, return null.
if (name.is_empty())
return nullptr;
auto elements = collect_matching_elements();
update_cache_if_needed();
auto const& elements = m_cached_elements;
// 2. Return the first element in the collection for which at least one of the following is true:
// - it has an ID which is key;
if (auto it = elements.find_if([&](auto& entry) { return entry->id().has_value() && entry->id().value() == name; }); it != elements.end())
@ -124,9 +128,8 @@ Vector<FlyString> HTMLCollection::supported_property_names() const
Vector<FlyString> result;
// 2. For each element represented by the collection, in tree order:
auto elements = collect_matching_elements();
for (auto& element : elements) {
update_cache_if_needed();
for (auto const& element : m_cached_elements) {
// 1. If element has an ID which is not in result, append element’s ID to result.
if (auto const& id = element->id(); id.has_value()) {
if (!result.contains_slow(id.value()))