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<!DOCTYPE html>
<html>
<body>
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<h1>JavaScript 比较</h1>
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<h2>() ? : 三元运算符</h2>
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<p>请输入您的年龄并单击按钮：</p>
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<input id="age" value="18" />
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<button onclick="myFunction()">试一试</button>
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<p id="demo"></p>
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<script>
function myFunction() {
  let age = document.getElementById("age").value;
  let voteable = (age < 18) ? "Too young":"Old enough";
  document.getElementById("demo").innerHTML = voteable + " to vote.";
}
</script>
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</body>
</html>
​