Object.freeze to freeze a property? Or how to set a property to be immutable/read-only?

Question

The docs for Object.freeze() state that it only allows freezing the object if its primitive type is actually "object". I'm working with some JSON data objects and was hoping to use this to set specific properties to be immutable (e.g. uuid, which is immutable in the db). Object.freeze() seemed like the perfect solution, until:

TypeError: Object.freeze called on non-object

Darn.

So, assuming I've got an object (parsed from JSON) like this:

{
    "uuid": "765926c1-911e-49b2-b597-48cf0df59a17",
    "firstName": "Bob",
    "lastName": "Dole"
}

is there any way I can force uuid to be immutable?

Answer 1

Yes, you need to use Object.defineProperty and re-define uuid property descriptor to be non-writable and non-configurable:

Object.defineProperty(obj, "uuid", { configurable: false, writable: false });

configurable: false means that from now uuid property descriptor can't be defined again. That is, no other sentence will be able to let the property be mutable again.

At the end of the day, Object.freeze is like a shortcut which iterates all enumerable properties in a given object and turns them into non-configurable+non-writable ones.