Heavy use of deprecated __proto__

[inca]

Don't know if this came up before, but I noticed heavy use of __proto__ throughout Express codebase, which is deprecated and seems to be heavily discouraged by MDN.

Now, since Express 4 is a fresh start, I was wondering if these fragments could be revisited, too? Frankly, I don't know if this even possible, or is there any good reason to stick with __proto__, so any explanations on this one would be very much appreciated.

[jonathanong]

reopen this issue when we can do Object.setPrototypeOf() in all supported versions of node. there's not much we can do about it now.

[rlidwka]

reopen this issue when we can do Object.setPrototypeOf() in all supported versions of node.

polyfill?

[inca]

Any insights on how Object.setPrototypeOf is any better, performance-wise? AFAIK it is not the __proto__ itself which is discouraged, it is mutating object prototype once it is created.

Citing from MDN:

Mutating the [[Prototype]] of an object is, by the nature of how modern JavaScript engines optimize property accesses, a very slow operation. If you care at all about performance, you should never mutate the [[Prototype]] of an object, either using this method or using Object.setPrototypeOf. Instead, create the object with the desired [[Prototype]] using Object.create.

[rlidwka]

AFAIK it is not the __proto__ itself which is discouraged

__proto__ itself is discouraged, because it prevents an arbitrary object to be safely used as a dictionary. Performance is the same obviously.

[inca]

I don't have any arguments to this statement. I am only concerned about MDN mentioning slowing down property access after using either __proto__ or Object.setPrototypeOf.