javascript hasclass

if (document.body.classList.contains('thatClass')) {
    // do some stuff
}if (myElement.classList.contains('someClassname')) {
    // do something
}document.body.classList.add('thisClass');
// $('body').addClass('thisClass');

document.body.classList.remove('thatClass');
// $('body').removeClass('thatClass');

document.body.classList.toggle('anotherClass');
// $('body').toggleClass('anotherClass');$('.check-fields').on('click', function () {

    var reqlength = $('.required-entry').length;
    console.log(reqlength);
    var value = $('.required-entry').filter(function () {
        return this.value != '';
    });

    if (value.length>=0 && (value.length !== reqlength)) {
        alert('Please fill out all required fields.');
    } else {
        alert('Everything has a value.');
    }
});