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LibJS: Add spec step comments to Object.assign()

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Linus Groh 2021-07-05 17:20:12 +01:00
parent 4f2af65836
commit 2e94fa25d0
1 changed files with 25 additions and 2 deletions
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27
Userland/Libraries/LibJS/Runtime/ObjectConstructor.cpp
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@ -426,33 +426,56 @@ JS_DEFINE_NATIVE_FUNCTION(ObjectConstructor::has_own)
// 20.1.2.1 Object.assign ( target, ...sources ), https://tc39.es/ecma262/#sec-object.assign
JS_DEFINE_NATIVE_FUNCTION(ObjectConstructor::assign)
{
// 1. Let to be ? ToObject(target).
auto* to = vm.argument(0).to_object(global_object);
if (vm.exception())
return {};
// 2. If only one argument was passed, return to.
if (vm.argument_count() == 1)
return to;
// 3. For each element nextSource of sources, do
for (size_t i = 1; i < vm.argument_count(); ++i) {
auto next_source = vm.argument(i);
// a. If nextSource is neither undefined nor null, then
if (next_source.is_nullish())
continue;
// i. Let from be ! ToObject(nextSource).
auto from = next_source.to_object(global_object);
VERIFY(!vm.exception());
// ii. Let keys be ? from.[[OwnPropertyKeys]]().
auto keys = from->internal_own_property_keys();
if (vm.exception())
return {};
// iii. For each element nextKey of keys, do
for (auto& next_key : keys) {
auto property_name = PropertyName::from_value(global_object, next_key);
auto property_descriptor = from->internal_get_own_property(property_name);
if (!property_descriptor.has_value() || !*property_descriptor->enumerable)
// 1. Let desc be ? from.[[GetOwnProperty]](nextKey).
auto desc = from->internal_get_own_property(property_name);
// 2. If desc is not undefined and desc.[[Enumerable]] is true, then
if (!desc.has_value() || !*desc->enumerable)
continue;
// a. Let propValue be ? Get(from, nextKey).
auto prop_value = from->get(property_name);
if (vm.exception())
return {};
// b. Perform ? Set(to, nextKey, propValue, true).
to->set(property_name, prop_value, true);
if (vm.exception())
return {};
}
}
// 4. Return to.
return to;
}