js获取星期几

function getweek(time) {
    /*显示星期*/
    /*time为date格式*/
    var str;
    var d = time.getDay();
    switch (d) {
        case 0:
            str = 0;
            break;
        case 1:
            str = 1;
            break;
        case 2:
            str = 2;
            break;
        case 3:
            str = 3;
            break;
        case 4:
            str = 4;
            break;
        case 5:
            str = 5;
            break;
        case 6:
            str = 6;
            break;
    }
    return str;
}