// To check if something is a native error we need to check the
-// concrete native error types. It is not enough to check "obj
-// instanceof $Error" because user code can replace
-// NativeError.prototype.__proto__. User code cannot replace
-// NativeError.prototype though and therefore this is a safe test.
+// concrete native error types. It is not sufficient to use instanceof
+// since it possible to create an object that has Error.prototype on
+// its prototype chain. This is the case for DOMException for example.
function IsNativeErrorObject(obj) {
- return (obj instanceof $Error) ||
- (obj instanceof $EvalError) ||
- (obj instanceof $RangeError) ||
- (obj instanceof $ReferenceError) ||
- (obj instanceof $SyntaxError) ||
- (obj instanceof $TypeError) ||
- (obj instanceof $URIError);
+ switch (%_ClassOf(obj)) {
+ case 'Error':
+ case 'EvalError':
+ case 'RangeError':
+ case 'ReferenceError':
+ case 'SyntaxError':
+ case 'TypeError':
+ case 'URIError':
+ return true;
+ }
+ return false;
}