Comment by m0meni

Wouldn't this swallow errors that you wouldn't want it to swallow? e.g. you try to access a property on a value that's null (which you think isn't null), and instead of getting an error, nothing happens. Idx[0] is a way better solution to dealing with the boilerplate of checking for null/undefined that has 0 runtime cost due to being compiled away by babel. It works with type systems, and you can even use it as a babel macro[1].

With it

    idx(props, _ => _.user.friends[0].friends)

compiles to

    props.user == null ? props.user :
    props.user.friends == null ? props.user.friends :
    props.user.friends[0] == null ? props.user.friends[0] :
    props.user.friends[0].friends

Optional chaining[2] would add this to JS at the language level by using ?. as the operator.

[0]: https://github.com/facebookincubator/idx [1]: https://github.com/dralletje/idx.macro [2]: https://github.com/tc39/proposal-optional-chaining