<!DOCTYPE html> <html> <body> <h1>JavaScript 比较</h1> <h2>() ? : 三元运算符</h2> <p>请输入您的年龄并单击按钮:</p> <input id="age" value="18" /> <button onclick="myFunction()">试一试</button> <p id="demo"></p> <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> </body> </html>