У вашего броузера проблема в совместимости с HTML5
⚛️ In this video I take an example React app and migrate the UNSAFE_ lifecycle hooks to use safer alternatives
? NOTE: You technically don't need to migrate yet. The original methods won't be deprecated until a v16.x release or removed until v17
? Resources
https://twitter.com/elijahmanor
https://reactjs.org/blog/2018/03/27/update-on-async-rendering.html ⬅ React Blog Post
https://github.com/reactjs/rfcs/blob/master/text/0033-new-commit-phase-lifecycles.md ⬅ React RFC
https://gist.github.com/elijahmanor/be93d8829f8fb8ed460809256f8f5d00 ⬅ Code from Video