[Question] about "._owner.alternate"

[HOUCe]

It seems that in react@16 every React element children contains cyclic property ._owner.alternate.alternate.alternate.alternate....

So it is easy to cause "Maximum call stack exceeded" error when developer compares props.children in deep way(like deep-equal).

This caused bugs for community libraries like react-helmet:
nfl/react-helmet#441

I am extremely curious about:
Why React has _owner.alternate, and what it stands for?
As it is named as “_owner”, could it be better if we make “owner” not enumerable?

I tried to search source code and but still can’t find any clue.

Thanks in advance.

[threepointone]

._owner is part of the internal data structure (called a Fiber) that react uses to track components and its relationship to other elements in the tree. You probably shouldn't compare children when doing a prop comparison check inside shouldComponentUpdate, it's not meant to be used as a public api. It looks like react-helmet has a fix in its next version. closing this issue.