javascript獲取昨天日期

<script type="text/javascript">
    var date = new Date();
    var y = date.getFullYear();
    var m = date.getMonth() + 1;
    var d = date.getDate() - 1;
    if (d == "0") {
        m = m - 1;
        var temp = new Date(y, m, d);
        d = temp.getDate();
    }
    var Yesterday = [y, m, d];
    Yesterday = Yesterday.join("/");
    alert(Yesterday);
</script>