计时3秒后自动跳转到登录页

<script>
    //计时3秒后自动跳转到登录页
    var i = 3;
    var time_out;
    time_out = setInterval("time()", 800);
    function time() {
        if(i == 0){
            window.location.href = "/user/login";
            clearInterval(time_out);
        }
        document.getElementById("time").innerHTML = i;
        i--;
    }
</script>