var proxy = Proxy.revocable([], {}); proxy.revoke(); function shouldThrow(func, errorMessage) { var errorThrown = false; var error = null; try { func(); } catch (e) { errorThrown = true; error = e; } if (!errorThrown) throw new Error('not thrown'); if (String(error) !== errorMessage) throw new Error(`bad error: ${String(error)}`); } shouldThrow(() => { var string = new String("Hello"); string.toString = function () { throw new Error("Out"); }; JSON.stringify({}, proxy.proxy, string); }, `TypeError: Array.isArray cannot be called on a Proxy that has been revoked`); shouldThrow(() => { var string = new String("Hello"); string.toString = function () { throw new Error("Out"); }; JSON.stringify({}, [], string); }, `Error: Out`);