3.25js作业

<!DOCTYPE html>
<html>
<head>
<title>是闰年</title>
</head>
<body>
<script>

var years = 1998;
if (years%4!=0) {
alert('不是闰年')
}else  if (years%100!=0)
{
alert('不是闰年')
}else{
alert('不是闰年')
}
</script>
</body>
<ml>

<!DOCTYPE html>
<html>
<head>
</head>
<body>
<script type="text/javascript">

var grade = 89;
if (grade>90||grade<=100) {
alert('成绩优秀');
}else  if (grade>=80||grade<=90) {
alert('成绩良好');
}else  if (grade>=70||grade<=79) {
alert('成绩良');
}else  if (grade>=60||grade<=69) {
alert('成绩及格');
}else{
alert('成绩不及格');
}

</script>

</body>
<ml>

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