1. React strict mode. StrictMode is a tool for highlighting potential problems in an application. Like Fragment, StrictMode does not render any visible UI. It activates additional checks and warnings for its descendants.
StrictMode currently helps with
- Identifying components with unsafe lifecycles.
- Warning about legacy string ref API usage
- Warning about deprecated findDOMNode usage
- Detecting unexpected side effects
- Detecting legacy context API
- Ensuring reusable state
2. Source Map Creates link between compiled output file and source file. Helps to debug easy in case of an error in browser - In dev mode It is a best practises to hide the source map in production mode to prevent accessing the source code.