function scroll(scrollTo, time) {
var scrollFrom = parseInt(document.body.scrollTop),
i = 0,
runEvery = 5; // run every 5ms
scrollTo = parseInt(scrollTo);
time /= runEvery;
var interval = setInterval(function () {
i++;
document.body.scrollTop = (scrollTo - scrollFrom) / time * i + scrollFrom;
if (i >= time) {
clearInterval(interval);
}
}, runEvery);
}
$('#trigger').click(function () {
scroll('600px', 500);
});