how to check if a element has a class jquery code example

Example 1: javascript hass class

if (myElement.classList.contains('someClassname')) {
    // do something
}

Example 2: jquery hasclass

$( "#mydiv" ).hasClass( "foo" )

Example 3: jquery select input value empty and hasclass

$('.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.');
    }
});