The Angular Template Syntax includes a safe navigation operator which works like this proposed operator. See: https://angular.io/guide/template-syntax#safe-navigation-operator

It seems appropriate that this should be listed in the prior art of this proposal, in particular because the template syntax is based on Javascript and is therefore closer to home than the other languages listed. Also it may be advisable to be take note of any differences in the semantics between the two if they exist.