Say I created an object like this
var obj = {M:"soober"};
its [[Prototype]] internal property points to Object.prototype.
Now, if I run...
Object.seal(Object.prototype);
...does this make all objects in the program immutable?
I need some clarity in this matter.
Lets see:
> var b = Object.create(Object.seal({}));
> b.foo = 'bar';
> b.foo
"bar"
...does this make all objects in the program immutable?
No.
From the MDN documentation:
The
Object.seal()method seals an object, preventing new properties from being added to it and marking all existing properties as non-configurable. Values of present properties can still be changed as long as they are writable.
Since b is not sealed (its prototype is), there is no problem adding new properties to it.
Object.freeze, not Object.sealFor such simple things I would recommend simply trying them out on the console and/or reading the docs
(() => {let prot = Object.create(null); let instance = Object.create(prot); Object.freeze(prot); instance.foo = "bar"; console.log(instance)})();. descendant can be modified with a frozen prototype.{ let a = Object.freeze({foo: 'foo'}); let b = Object.create(a); b.foo = 'bar'; console.log(b); }.The Object.seal() method seals an object, preventing new properties from being added to it and marking all existing properties as non-configurable. Values of present properties can still be changed as long as they are writable.
The prototype is a separate object, whose properties are only queried if no such property is found in the object itself (and so on, down the prototype chain).
Therefore sealing the prototype only prevents new properties from being added to the prototype itself, and has no effect on whether properties can be added to other objects that inherit from that prototype.
