几月几号+星期几格式化

<div id="mDayWeek">9月29日 星期五</div>

<script>
    week('mDayWeek');
    //几月几号+星期几
    function week(id) {
        var obj = window.document.getElementById(id);
        var date = new Date();
        var month = date.getMonth()+1;//月
        var day = date.getDate();//日
        var data = date.getDay();//星期几
        switch(data){
            case 0:
                weeks="星期日";
                break;
            case 1:
                weeks="星期一";
                break;
            case 2:
                weeks="星期二";
                break;
            case 3:
                weeks="星期三";
                break;
            case 4:
                weeks="星期四";
                break;
            case 5:
                weeks="星期五";
                break;
            case 6:
                weeks="星期六";
                break;
        }
        obj.innerHTML= month + '月' + day + '日' + ' ' + weeks;
    }


</script>