javascript学习代码-判断闰年

<!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>

 

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