Button toggle class

HTML

<button type="button" class="clickBtn">Click Me</button>
<div class="hiddenDiv"> This is the hidden text. </div>

CSS

button {
    background-color: green;
}
button.btnWorking {
    background-color: red;
}

JavaScript

var asyncData = false;

$('.hiddenDiv').hide();

$(".clickBtn").click( function(evt) {
    if ( $(this).hasClass('btnWorking') ) {
        $(this).removeClass('btnWorking');
        $('.hiddenDiv').hide();
    } else {
        $(this).addClass('btnWorking');
        $('.hiddenDiv').show();
        if (!asyncData) {
            $.ajax({
                url: '/echo/html/',
                data: {
                    html: '<p>This is the ajax HTML</p>',
                    delay: 2
                },
                method: 'post'
            }).done( function(data) {
                asyncData = data;
                $('.hiddenDiv').append(data);
            });
        }
    }
});