TypeError: Immutable prototype object 'Object.prototype' cannot have their prototype set (V8-based)TypeError: #<Object> is not extensible (V8-based)TypeError: can't set prototype of this object (Firefox)TypeError: Cannot set prototype of immutable prototype object (Safari)TypeError: Attempted to assign to readonly property. (Safari)

You are using one of the prototype-mutating methods—most notably,Object.setPrototypeOf()—on an object whose prototype is immutable. Some built-in objects have immutable prototypes, such asObject.prototype andwindow, for security reasons. User objects can also prevent prototype changes by usingObject.preventExtensions(),Object.seal(), orObject.freeze().

A selected few built-in objects have immutable prototypes. For example, you cannot change the prototype ofObject.prototype:

Object.setPrototypeOf(Object.prototype, {});

This prevents you from being able to arbitrarily change the behavior of all objects in the system. The prototype ofObject.prototype is alwaysnull. However, other built-in prototype objects, such asFunction.prototype andArray.prototype, are not protected by default in this regard.

If you make an object non-extensible, you cannot change its prototype either:

const obj = {};Object.preventExtensions(obj);Object.setPrototypeOf(obj, {});// TypeError: can't set prototype of this object

• Object.setPrototypeOf()
• Object.preventExtensions()