bool JSArray::getOwnPropertyDescriptor(JSObject* object, ExecState* exec, PropertyName propertyName, PropertyDescriptor& descriptor)
{
JSArray* thisObject = jsCast<JSArray*>(object);
if (propertyName == exec->propertyNames().length) {
descriptor.setDescriptor(jsNumber(thisObject->length()), thisObject->isLengthWritable() ? DontDelete | DontEnum : DontDelete | DontEnum | ReadOnly);
return true;
}
return JSObject::getOwnPropertyDescriptor(thisObject, exec, propertyName, descriptor);
}
bool JSArray::getOwnPropertySlot(JSObject* object, ExecState* exec, PropertyName propertyName, PropertySlot& slot)
{
JSArray* thisObject = jsCast<JSArray*>(object);
if (propertyName == exec->propertyNames().length) {
unsigned attributes = thisObject->isLengthWritable() ? DontDelete | DontEnum : DontDelete | DontEnum | ReadOnly;
slot.setValue(thisObject, attributes, jsNumber(thisObject->length()));
return true;
}
return JSObject::getOwnPropertySlot(thisObject, exec, propertyName, slot);
}
// Defined in ES5.1 15.4.5.1
bool JSArray::defineOwnProperty(JSObject* object, ExecState* exec, PropertyName propertyName, const PropertyDescriptor& descriptor, bool throwException)
{
JSArray* array = jsCast<JSArray*>(object);
// 3. If P is "length", then
if (propertyName == exec->propertyNames().length) {
// All paths through length definition call the default [[DefineOwnProperty]], hence:
// from ES5.1 8.12.9 7.a.
if (descriptor.configurablePresent() && descriptor.configurable())
return reject(exec, throwException, "Attempting to change configurable attribute of unconfigurable property.");
// from ES5.1 8.12.9 7.b.
if (descriptor.enumerablePresent() && descriptor.enumerable())
return reject(exec, throwException, "Attempting to change enumerable attribute of unconfigurable property.");
// a. If the [[Value]] field of Desc is absent, then
// a.i. Return the result of calling the default [[DefineOwnProperty]] internal method (8.12.9) on A passing "length", Desc, and Throw as arguments.
if (descriptor.isAccessorDescriptor())
return reject(exec, throwException, "Attempting to change access mechanism for an unconfigurable property.");
// from ES5.1 8.12.9 10.a.
if (!array->isLengthWritable() && descriptor.writablePresent() && descriptor.writable())
return reject(exec, throwException, "Attempting to change writable attribute of unconfigurable property.");
// This descriptor is either just making length read-only, or changing nothing!
if (!descriptor.value()) {
if (descriptor.writablePresent())
array->setLengthWritable(exec, descriptor.writable());
return true;
}
// b. Let newLenDesc be a copy of Desc.
// c. Let newLen be ToUint32(Desc.[[Value]]).
unsigned newLen = descriptor.value().toUInt32(exec);
// d. If newLen is not equal to ToNumber( Desc.[[Value]]), throw a RangeError exception.
if (newLen != descriptor.value().toNumber(exec)) {
exec->vm().throwException(exec, createRangeError(exec, ASCIILiteral("Invalid array length")));
return false;
}
// Based on SameValue check in 8.12.9, this is always okay.
// FIXME: Nothing prevents this from being called on a RuntimeArray, and the length function will always return 0 in that case.
if (newLen == array->length()) {
if (descriptor.writablePresent())
array->setLengthWritable(exec, descriptor.writable());
return true;
}
// e. Set newLenDesc.[[Value] to newLen.
// f. If newLen >= oldLen, then
// f.i. Return the result of calling the default [[DefineOwnProperty]] internal method (8.12.9) on A passing "length", newLenDesc, and Throw as arguments.
// g. Reject if oldLenDesc.[[Writable]] is false.
if (!array->isLengthWritable())
return reject(exec, throwException, "Attempting to change value of a readonly property.");
// h. If newLenDesc.[[Writable]] is absent or has the value true, let newWritable be true.
// i. Else,
// i.i. Need to defer setting the [[Writable]] attribute to false in case any elements cannot be deleted.
// i.ii. Let newWritable be false.
// i.iii. Set newLenDesc.[[Writable] to true.
// j. Let succeeded be the result of calling the default [[DefineOwnProperty]] internal method (8.12.9) on A passing "length", newLenDesc, and Throw as arguments.
// k. If succeeded is false, return false.
// l. While newLen < oldLen repeat,
// l.i. Set oldLen to oldLen – 1.
// l.ii. Let deleteSucceeded be the result of calling the [[Delete]] internal method of A passing ToString(oldLen) and false as arguments.
// l.iii. If deleteSucceeded is false, then
if (!array->setLength(exec, newLen, throwException)) {
// 1. Set newLenDesc.[[Value] to oldLen+1.
// 2. If newWritable is false, set newLenDesc.[[Writable] to false.
// 3. Call the default [[DefineOwnProperty]] internal method (8.12.9) on A passing "length", newLenDesc, and false as arguments.
// 4. Reject.
if (descriptor.writablePresent())
array->setLengthWritable(exec, descriptor.writable());
return false;
}
// m. If newWritable is false, then
// i. Call the default [[DefineOwnProperty]] internal method (8.12.9) on A passing "length",
// Property Descriptor{[[Writable]]: false}, and false as arguments. This call will always
// return true.
if (descriptor.writablePresent())
array->setLengthWritable(exec, descriptor.writable());
// n. Return true.
return true;
}
// 4. Else if P is an array index (15.4), then
// a. Let index be ToUint32(P).
if (Optional<uint32_t> optionalIndex = parseIndex(propertyName)) {
// b. Reject if index >= oldLen and oldLenDesc.[[Writable]] is false.
uint32_t index = optionalIndex.value();
// FIXME: Nothing prevents this from being called on a RuntimeArray, and the length function will always return 0 in that case.
if (index >= array->length() && !array->isLengthWritable())
return reject(exec, throwException, "Attempting to define numeric property on array with non-writable length property.");
// c. Let succeeded be the result of calling the default [[DefineOwnProperty]] internal method (8.12.9) on A passing P, Desc, and false as arguments.
// d. Reject if succeeded is false.
// e. If index >= oldLen
// e.i. Set oldLenDesc.[[Value]] to index + 1.
// e.ii. Call the default [[DefineOwnProperty]] internal method (8.12.9) on A passing "length", oldLenDesc, and false as arguments. This call will always return true.
// f. Return true.
return array->defineOwnIndexedProperty(exec, index, descriptor, throwException);
}
return array->JSObject::defineOwnNonIndexProperty(exec, propertyName, descriptor, throwException);
}