const obj = Object.seal({ a: 1, b: { c: 2 } });
obj.a = 10;
obj.b.c = 20;
obj.d = 30;
delete obj.a;

const frozen = Object.freeze({ x: 5, y: { z: 10 } });
frozen.x = 50;
frozen.y.z = 100;
delete frozen.y;

console.log(obj.a, obj.b.c, obj.d, frozen.x, frozen.y.z);