Lifecycle / Dev-mode warnings
Dev-mode warnings
Misuse that would otherwise fail silently in production is reported at the point of use, in development only.
What gets flagged
SITUATIONWHY IT MATTERS
value and defaultValue both passedThe component cannot be both controlled and uncontrolled
value passed with no onChangeThe field will appear frozen to the user
A constraint that can never passmin above max is a typo, not a rule
name missing inside a <form>FormData will not carry the value
Stripped in production
The warnings sit behind a process.env.NODE_ENV !== "production" check and each one fires at most once per component instance, so a warning in a list of two hundred rows does not produce two hundred lines of console noise.