<!doctype html> <html> <head> <title>年月日</title> </head> <body onLoad="init()"> <select id="year" onChange="swap_day()"></select>年 <select id="month" onChange="swap_day()"></select>月 <select id="day"></select>日 </body> <script> var month_big = new Array("1","3","5","7","8","10","12"); //包含所有大月的数组 var month_small = new Array("4","6","9","11"); //包含所有小月的数组 //页面加载时调用的初始化select控件的option的函数 function init() { var select_year = document.getElementById("year"); //获取id为"year"的下拉列表框 var select_month = document.getElementById("month"); //获取id为"month"的下拉列表框 var select_day = document.getElementById("day"); //获取id为"day"的下拉列表框 //将年份选项初始化，从1980到2000 for(var i = 1980; i <= 2000; i++) { select_year_option = new Option(i, i); select_year.options.add(select_year_option); } //将月份选项初始化，从1到12 for(var i = 1; i <= 12; i++) { select_month_option = new Option(i, i); select_month.options.add(select_month_option); } //调用swap_day函数初始化日期 swap_day(); } //判断数组array中是否包含元素obj的函数，包含则返回true，不包含则返回false function array_contain(array, obj) { for (var i = 0; i < array.length; i++) { if (array[i] === obj) { return true; } } return false; } //根据年份和月份调整日期的函数 function swap_day() { var select_year = document.getElementById("year"); //获取id为"year"的下拉列表框 var select_month = document.getElementById("month"); //获取id为"month"的下拉列表框 var select_day = document.getElementById("day"); //获取id为"day"的下拉列表框 select_day.options.length = 0; //在调整前先清空日期选项里面的原有选项 var month = select_month.options[select_month.selectedIndex].value; //获取被选中的月份month //如果month被包含在month_big数组中，即被选中月份是大月，则将日期选项初始化为31天 if(array_contain(month_big, month)) { for(var i = 1; i <= 31; i++) { select_day_option = new Option(i, i); select_day.options.add(select_day_option); } } //如果month被包含在month_small数组中，即被选中月份是小月，则将日期选项初始化为30天 else if(array_contain(month_small, month)) { for(var i = 1; i <= 30; i++) { select_day_option = new Option(i, i); select_day.options.add(select_day_option); } } //如果month为2，即被选中的月份是2月，则调用initFeb()函数来初始化日期选项 else { initFeb(); } } //判断年份year是否为闰年，是闰年则返回true，否则返回false function isLeapYear(year) { var a = year % 4; var b = year % 100; var c = year % 400; if( ( (a == 0) && (b != 0) ) || (c == 0) ) { return true; } return false; } //根据年份是否闰年来初始化二月的日期选项 function initFeb() { var select_year = document.getElementById("year"); //获取id为"year"的下拉列表框 var select_day = document.getElementById("day"); //获取id为"day"的下拉列表框 var year = parseInt(select_year.options[select_year.selectedIndex].value); //获取被选中的年份并转换成Int //如果是闰年，则将日期选项初始化为29天 if(isLeapYear(year)) { for(var i = 1; i <= 29; i++) { select_day_option = new Option(i, i); select_day.options.add(select_day_option); } } //如果不是闰年，则将日期选项初始化为28天 else { for(var i = 1; i <= 28; i++) { select_day_option = new Option(i, i); select_day.options.add(select_day_option); } } } </script> </html>