JS当前日期相加相减

function DateAddORSub(interval,type,number)
{
/*
 * 功能:实现Script的Date加减功能.
 * 参数:interval,字符串表达式，表示要添加的时间间隔.
 * 参数:number,数值表达式，表示要添加的时间间隔的个数.
 * 参数:type,加减类型.
 * 返回:新的时间对象.
 * var newDate =DateAddORSub("d","+",5);
 */
  var date = new Date();
    switch(interval)
    {
        case "y" : {
		    if(type=="+"){
             date.setFullYear(date.getFullYear()+number);
			}else{
			 date.setFullYear(date.getFullYear()-number);
			}
            return date;
            break;
        }
        case "q" : {
		    if(type=="+"){
            date.setMonth(date.getMonth()+number*3);
			}else{
			 date.setMonth(date.getMonth()-number*3);
			}
            return date;
            break;
        }
        case "m" : {
		    if(type=="+"){
             date.setMonth(date.getMonth()+number);
			}else{
			 date.setMonth(date.getMonth()-number);
			}
            return date;
            break;
        }
        case "w" : {
		    if(type=="+"){
            date.setDate(date.getDate()+number*7);
			}else{
			date.setDate(date.getDate()-number*7);
			}
            return date;
            break;
        }
        case "d" : {
		    if(type=="+"){
             date.setDate(date.getDate()+number);
			}else{
			  date.setDate(date.getDate()-number);
			}
            return date;
            break;
        }
        case "h" : {
		     if(type=="+"){
            date.setHours(date.getHours()+number);
			}else{
			 date.setHours(date.getHours()-number);
			}
            return date;
            break;
        }
        case "m" : {
		    if(type=="+"){
            date.setMinutes(date.getMinutes()+number);
			}else{
			date.setMinutes(date.getMinutes()-number);
			}
            return date;
            break;
        }
        case "s" : {
		     if(type=="+"){
            date.setSeconds(date.getSeconds()+number);
			}else{
			 date.setSeconds(date.getSeconds()-number);
			}
            return date;
            break;
        }
        default : {
		     if(type=="+"){
             date.setDate(d.getDate()+number);
			}else{
			 date.setDate(d.getDate()-number);
			}
            return date;
            break;
        }
    }
}

function formatDate(date){;
   var year = date.getFullYear();    //年
   var month = date.getMonth() + 1;   //月
   var day = date.getDate();      //日
   return year+"-"+month+"-"+day;
}

//当前时间加五天. 
var newDate = DateAddORSub("d","+",5); 
alert(newDate.toLocaleDateString()); 
//当前时间减五天. 
newDate = DateAddORSub("d","-",5); 
alert(formatDate(newDate)); 
//当前时间加两个月. 
newDate = DateAddORSub("m","+",2); 
alert(newDate.toLocaleDateString()); 
//当前时间减两个月. 
newDate = DateAddORSub("m","-",2); 
alert(formatDate(newDate)); 
//当前时间加一年 
newDate = DateAddORSub("y","+",1); 
alert(newDate.toLocaleDateString()); 
//当前时间减一年 
newDate = DateAddORSub("y","-",1); 
alert(formatDate(newDate));