How to correctly catch change/focusOut event on text input in React.js?

If you want to only trigger validation when the input looses focus you can use onBlur.

React uses onFocus and onBlur instead of onFocusIn and onFocusOut. All React events are normalized to bubble, so onFocusIn and onFocusOut are not needed/supported by React. 2

Its late, yet it's worth your time nothing that, there are some differences in browser level implementation of focusin and focusout events and react synthetic onFocus and onBlur. focusin and focusout actually bubble, while onFocus and onBlur dont. So there is no exact same implementation for focusin and focusout as of now for react. Anyway most cases will be covered in onFocus and onBlur.

JavaScript => React

onfocusout => onBlur

onfocusin => onFocus