SO - 21312218

by Arun P Johny

HTML

<div class="wrap">
    <input id="test-1" type="radio" name="testing" checked />
    <input id="test-2" type="radio" name="testing" />
    <input id="test-3" type="radio" name="testing" />
</div>
<button id="start-stop">Start/stop</button>

JavaScript

jQuery(function () {
    var timer;
    $("#start-stop").click(function () {
        if (timer) {
            clearInterval(timer);
            timer = undefined;
        } else {
            timer = setInterval(function () {
                $('.wrap input')
                    .eq(($('input:checked').index() + 1) % 3)
                    .prop('checked', true);
            }, 1000);
        }
    });
})