JSFiddle - React, Tailwind, and code Playground

HTML

<p><input type="text" /></p>
<p><input type="text" /></p>
<p><input id="email" type="text" /></p>
<p><input type="text" /></p>

JavaScript

var errors = [];

$('input').not('#email').each(function() {
    if($(this).val() == '') {
        errors.push(this);
    }    
});

$('#email').each(function() {
    var pregstr = /^[a-zA-Z0-9._-]+@[a-zA-Z0-9.-]+\.[a-zAZ]{2,4}$/;
    
    if(!(pregstr.test($('#email').val()))) {
        errors.push(this);   
    }
});

$(errors).css('background-color', 'red');