CODEWITHSUNDEEP
javascriptclassobject
pablo pento
pablo pento

Reputation: 45

[Class].prototype can be changed, despite Object.freeze([Class])

I created a class Money intended to be immutable as follow

    class Money{ 
             constructor(currency, amount)
             {
                 // this.curre... 
                 Object.freeze(this) // new instances are immutable
             }
     }

     // after that i want the [[Prototype]] of class.prototype to be null 
     Object.setPrototypeOf(Money.prototype,null)

     // to be sure that my class's prototype is not going to be changed
     Object.freeze(Money)

but

     Object.setPrototypeOf(Money.prototype, {}) //
     console.log(Money.prototype) // I got {}

     // I must add Object.freeze(Money.prototype) ???

prototype isn't really property of a class / Constructor function?

Upvotes: 0

Views: 58

Answers (1)

Pointy
Pointy

Reputation: 413737

Object.freeze() only affects the object you pass to it. It does not transitively freeze all objects that are values of properties.

If you have an object a:

let a = {
  b: {
    c: "Hello";
  }
};

then it would be pretty surprising if Object.freeze(a) made it impossible to change properties of a.b, because that's a different object.

Beyond that, it would be vastly more surprising if freezing one instance of a constructor would also result in the prototype of the constructor to be frozen.

Upvotes: 2

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