// Alter the submitted value in $form_state.
$form_state->setValueForElement($form['name'], 'value changed by setValueForElement() in #validate');
// Output the element's value from $form_state.
// Alter the submitted value in $form_state.
$form_state->setValueForElement($form['name'], 'value changed by setValueForElement() in #validate');
// Output the element's value from $form_state.