this is the address of this chapter: https://reactjs.org/docs/lift.
Chinese address: http://www.css88.com/react/do.

this chapter, called State Enhancement, is about how to use React to achieve a two-way binding, converting input degrees Celsius to Fahrenheit and input Fahrenheit to degrees Fahrenheit.

finally, this error will be reported after typing it out according to the source code

if (Number.isNaN(input)) {
return "";
}

NaN..

create-react-app

Thank you, all React bosses, Trout, please help me ~