// 计算系统当前是星期几  
    var str = ""; 
    var week = new Date().getDay();  
    if (week == 0) { 
        str = "今天是星期日";  
    } else if (week == 1) {
    str = "今天是星期一";  
    } else if (week == 2) {
        str = "今天是星期二";   
    } else if (week == 3) {
        str = "今天是星期三";   
    } else if (week == 4) {
        str = "今天是星期四";   
    } else if (week == 5) {
        str = "今天是星期五";   
    } else if (week == 6) {
        str = "今天是星期六";   
    }  
    // 或者更好一些  
    var str1 = "今天是星期"; 
    var week = new Date().getDay();  
    switch (week) {          
    case 0 : 
             str1 += "日";                  
             break;         
    case 1 : 
             str1 += "一";                 
             break;          
    case 2 : 
             str1 += "二";                  
             break;          
    case 3 : 
             str1 += "三";                  
             break;          
    case 4 : 
             str1 += "四";  
             break;          
    case 5 : 
             str1 += "五";             
             break;        
    case 6 : 
             str1 += "六";       
             break;  
    }  
    alert(str);  
    alert(str1); 

    var a = new Array("日", "一", "二", "三", "四", "五", "六");  
    var week = new Date().getDay(); 
    var str = "今天是星期"+ a[week];  
    alert(str); 

    // 计算系统当前是星期几  
    var str = "今天是星期" + "日一二三四五六".charAt(new Date().getDay());