`substr()` is deprecated and is not part of the core JS since ~2018. No wonder why no one noticed this :) Reference: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/substr So, I've refactored whole codebase to not use `substr()` and use `slice()` instead here: PR ~`#TBA`~ #37136 _Originally posted by @Pranav-yadav in https://github.com/facebook/react-native/pull/35993#discussion_r1180053127_