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<meta charset="UTF-8">
<meta name="viewport" content="width=, initial-scale=1.0">
<title>Document</title>
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<body>
<h2 id="res"></h2>
<!-- 条件判断 -->
<script>
var age =20;
if(age<30)
{
document.getElementById("res").innerHTML="年轻";
}
if (age>18 && age<30)
{
document.getElementById("res").innerHTML="最好学习年龄";
}
else if( age > 30 && age <= 40)
{
document.getElementById("res").innerHTML="最好学习年龄";
}
else
{
document.getElementById("res").innerHTML="暂未考虑";
}
</script>
</body>
</html>
