til/react/conditionally-including-event-handler-functions.md

Conditionally Including Event Handler Functions

React makes a variety of synthetic DOM events available to your component. Events such as onClick, onKeyPress, onSubmit, etc. When specifying one of these event handlers, you must supply a function.

To conditionally include an event handler, you may be tempted to do this:

<Toggler
  onKeyPress={someCondition && handleKeyPress}
/>

This means that onKeyPress will receive false when someCondition is false. That is a prop type violation. Instead, you should use a ternary statement.

<Toggler
  onKeyPress={someCondition ? handleKeyPress : undefined}
/>

If someCondition is false, then the prop will be set as undefined and that prop won't be defined.