javascript 年月日联动实现核心代码

var startyear = 1980;
var endyear = 2500;

function monthandday()
{
this.initddl = function(objyear,objmonth,objday,hidyear,hidmonth,hidday)
{
this.init(objyear,objmonth,objday,hidyear,hidmonth,hidday);
this.selectchange(objyear,objmonth,objday,hidyear,hidmonth,hidday);
}

this.init = function(objyear,objmonth,objday,hidyear,hidmonth,hidday)
{
var year = document.getelementbyid(objyear);
var month = document.getelementbyid(objmonth);
var day = document.getelementbyid(objday);
var me=this;

if(year.length == 1)
{
year.options[0] = new option("不限","");
for(var i = startyear; i < endyear; i++)
{
year.options[year.length] = new option(i,i);
}
}
me.yearoptionschange(document.all[objyear].value,objyear,objmonth,objday);
me.monthoptionschange(document.all[objyear].value,document.getelementbyid(objmonth).value,objday);
}

this.yearoptionschange = function(selectvalue,objyear,objmonth,objday)
{
var month = document.getelementbyid(objmonth);
var day = document.getelementbyid(objday);
var me=this;
month.length = 0;
day.length = 0;
month.options[0]=new option("不限",'');
day.options[0]=new option("不限",'');

if(selectvalue == "")
{
return ;
}

for(var i = 1; i < 13; i++)
{
month.options[month.length] = new option((i < 10 ? ("0" + i) : i),i);
}
me.monthoptionschange(document.getelementbyid(objyear).value,document.getelementbyid(objmonth).value,objday);
}

this.monthoptionschange = function(yearselectvalue,monthselectvalue,objday)
{
var day = document.getelementbyid(objday);
var endday;
day.length = 0;

day.options[0]=new option("不限",'');

if(monthselectvalue == "")
{
return;
}
if((parseint(yearselectvalue) % 400 == 0) || (parseint(yearselectvalue) % 4 == 0 && parseint(yearselectvalue) % 100 != 0))
{
if(parseint(monthselectvalue) == "2")
{
endday = 29;
}
}
else
{
if(parseint(monthselectvalue) == "2")
{
endday = 28;
}
}
switch(parseint(monthselectvalue))
{
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
endday = 31;
break;
case 4:
case 6:
case 9:
case 11:
endday = 30;
break;
}

for(var i = 1; i <= endday; i++)
{
day.options[day.length] = new option((i < 10 ? ("0" + i) : i),i);
}
}

this.selectchange = function(objyear,objmonth,objday,hidyear,hidmonth,hidday)
{
var year = document.all[objyear];
var month = document.all[objmonth];
var day = document.all[objday];
var me = this;

year.onchange = function()
{
me.yearoptionschange(this.options[this.selectedindex].value,objyear,objmonth,objday);
document.all[hidyear].value = this.options[this.selectedindex].value;
document.all[hidmonth].value = "";
document.all[hidday].value = "";
}

month.onchange = function()
{
me.monthoptionschange(document.all[hidyear].value,this.options[this.selectedindex].value,objday);
document.all[hidmonth].value = this.options[this.selectedindex].value;
document.all[hidday].value = "";
}

day.onchange = function()
{
document.all[hidday].value = day.selectvalue;
}
}
}