I think you need something like this:
var sync_db_btn = document.getElementById('but'),
abortSync = -1,
interval,
sync_database = function () {
var i = 0;
abortSync *= -1;
if (abortSync < 0) {
sync_db_btn.innerHTML = 'Sync DB';
clearInterval(interval);
return false;
}
sync_db_btn.innerHTML = 'Abort';
interval = setInterval(function () {
if (i < 10) {
sync_db_btn.innerHTML = 'Abort ' + i++;
} else {
sync_db_btn.innerHTML = 'Sync DB';
clearInterval(interval);
abortSync = -1;
}
}, 1000);
};
sync_db_btn.addEventListener('click', sync_database);