Client side email verification using HTML, CSS and Vanilla JavaScript

I encountered an issue when submitting the form with an empty input.

The function briefly displays the error icon and message and then stops, making the error icon and message disappear after the page automatically reloads. I managed to find a solution using 'return false' as the form 'onsubmit' attribute value.

Nevertheless, I can't help but wonder if there is a better way of solving this. Feedback is highly appreciated.

Thanks.