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@ -82,7 +82,7 @@ Why was `__proto__` replaced by the functions `getPrototypeOf/setPrototypeOf`? T
```warn header="Don't change `[[Prototype]]` on existing objects if speed matters" ```warn header="Don't change `[[Prototype]]` on existing objects if speed matters"
Technically, we can get/set `[[Prototype]]` at any time. But usually we only set it once at the object creation time, and then do not modify: `rabbit` inherits from `animal`, and that is not going to change. Technically, we can get/set `[[Prototype]]` at any time. But usually we only set it once at the object creation time, and then do not modify: `rabbit` inherits from `animal`, and that is not going to change.
And JavaScript engines are highly optimized to that. Changing a prototype "on-the-fly" with `Object.setPrototypeOf` or `obj.__proto__=` is a very slow operation, it breaks internal optimizations for object property access operations. So evade it unless you know what you're doing, or JavaScript speed totally doesn't matter for you. And JavaScript engines are highly optimized for this. Changing a prototype "on-the-fly" with `Object.setPrototypeOf` or `obj.__proto__=` is a very slow operation, it breaks internal optimizations for object property access operations. So evade it unless you know what you're doing, or JavaScript speed totally doesn't matter for you.
``` ```
## "Very plain" objects [#very-plain] ## "Very plain" objects [#very-plain]