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LibJS: Implement the "instanceof" operator

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This operator walks the prototype chain of the RHS value and looks for
a "prototype" property with the same value as the prototype of the LHS.

This is pretty cool. :^)
This commit is contained in:
Andreas Kling 2020-03-28 16:56:54 +01:00
parent 37fe16a99c
commit a3d92b1210
6 changed files with 41 additions and 1 deletions
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22
Libraries/LibJS/Runtime/Value.cpp
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@ -24,6 +24,7 @@
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <AK/FlyString.h>
#include <AK/String.h>
#include <LibJS/Heap/Heap.h>
#include <LibJS/Runtime/Object.h>
@ -253,6 +254,27 @@ Value eq(Value lhs, Value rhs)
return Value(false);
}
Value instance_of(Value lhs, Value rhs)
{
if (!lhs.is_object() || !rhs.is_object())
return Value(false);
auto* instance_prototype = lhs.as_object()->prototype();
if (!instance_prototype)
return Value(false);
for (auto* constructor_object = rhs.as_object(); constructor_object; constructor_object = constructor_object->prototype()) {
auto prototype_property = constructor_object->get_own_property(*constructor_object, "prototype");
if (!prototype_property.has_value())
continue;
if (prototype_property.value().is_object() && prototype_property.value().as_object() == instance_prototype)
return Value(true);
}
return Value(false);
}
const LogStream& operator<<(const LogStream& stream, const Value& value)
{
return stream << value.to_string();