var submit = window.document.getElementById ('submit');
    submit.onclick = function () {
        window.localStorage.submit = 'wait';
        wait ();
    };

function wait () {
    if (window.localStorage.submit == 'wait') {
        var time = 15;
        var timer = window.setInterval ( function () {
            submit.value = time--;
            if (!time) {
                submit.value = 'Отправить';
                window.localStorage.submit = 'go';
                window.clearInterval (timer);
            }
        }, 1000);
    }
}