Validaciones
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<input type="email" id="correo" required pattern="^[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,4}$" />
https://regex101.com/
var input = document.getElementById('IdOfField'); var validityState_object = input.validity;
document.querySelector( "input" ) .addEventListener( "invalid", function( event ) { event.preventDefault(); });
Previene el comportamiento 'default'
Propiedad 'validity'
By Rodrigo Reyes