<html><head><title>年月日三下拉框联动</title><meta http-equiv='Content-Type' content='text/html; charset=gb2312'></head><body><form name=form1><select name=YYYY onchange="YYYYDD(this.value)"><option value="">请选择 年</option></select><select name=MM onchange="MMDD(this.value)"><option value="">选择 月</option></select><select name=DD><option value="">选择 日</option></select></form><script language="JavaScript">...<!--function YYYYMMDDstart()...{MonHead = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];//先给年下拉框赋内容var y = new Date().getFullYear();for (var i = (y-30); i < (y+30); i++) //以今年为准,前30年,后30年document.form1.YYYY.options.add(new Option(" "+ i +" 年", i));//赋月份的下拉框for (var i = 1; i < 13; i++)document.form1.MM.options.add(new Option(" " + i + " 月", i));document.form1.YYYY.value = y;document.form1.MM.value = new Date().getMonth() + 1;var n = MonHead[new Date().getMonth()];if (new Date().getMonth() ==1 && IsPinYear(YYYYvalue)) n++;writeDay(n); //赋日期下拉框Author:meizzdocument.form1.DD.value = new Date().getDate();}if(document.attachEvent)window.attachEvent("onload", YYYYMMDDstart);elsewindow.addEventListener('load', YYYYMMDDstart, false);function YYYYDD(str) //年发生变化时日期发生变化(主要是判断闰平年)...{var MMvalue = document.form1.MM.options[document.form1.MM.selectedIndex].value;if (MMvalue == "")...{ var e = document.form1.DD; optionsClear(e); return;}var n = MonHead[MMvalue - 1];if (MMvalue ==2 && IsPinYear(str)) n++;writeDay(n)}function MMDD(str) //月发生变化时日期联动...{var YYYYvalue = document.form1.YYYY.options[document.form1.YYYY.selectedIndex].value;if (YYYYvalue == "")...{ var e = document.form1.DD; optionsClear(e); return;}var n = MonHead[str - 1];if (str ==2 && IsPinYear(YYYYvalue)) n++;writeDay(n)}function writeDay(n) //据条件写日期的下拉框...{var e = document.form1.DD; optionsClear(e);for (var i=1; i<(n+1); i++)e.options.add(new Option(" "+ i + " 日", i));}function IsPinYear(year)//判断是否闰平年...{ return(0 == year%4 && (year%100 !=0 || year%400 == 0));}function optionsClear(e)...{e.options.length = 1;}//--></script></body></html>