<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob)</title>
</head>
<body>

<p>点击按钮检测年龄。</p>
年龄:<input id="age" value="18" />
<p>是否达到投票年龄?</p>
<button οnclick="myFunction()">点击按钮</button>
<p id="demo"></p>
<script>
function myFunction()
{
    var age,voteable;
    age=document.getElementById("age").value;
    voteable=(age<18)?"年龄太小":"年龄已达到";
    document.getElementById("demo").innerHTML=voteable;
}
</script>

</body>
</html>

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