<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <title>判断闰年与否</title> </head> <body> <script language="javascript" type="text/javascript"> function checkYear(){ var txtObjYear = document.all.txtYear; var txtYear = txtObjYear.value(); if ((txtObjYear == null) || (txtObjYear.length < 1) || (txtObjYear <0 )){ window.alert("请在文本框输入正确的年份！"); txtObjYear.focus(); return; } if (isNaN(txtYear))//用户输入的不是值 { window.alert("您输入的不是有效的数字！"); txtObjYear.focus(); return; } if (isLeapYear(txtYear)) window.alert(txtYear+"闰年！"); else window.alert(txtYear+"不是闰年！"); } function isLeapYear(yearVal){ if((yearVal % 100 == 0 ) && (yearVal % 400 == 0)) return true; if(yearVal % 4 == 0) return true; return false; } </script> <form action="#" name="frmYear"> <p>请输入当前年份： <input name="txtYear" type="text" /> <p>点击判断是不是闰年： <input type="button" value="submit" onclick="checkYear()" /> </form> </body> </html>