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));