<!DOCTYPE html>charset="utf-8"W3Cschool教程(w3cschool.cn)输入你的年龄并点击按钮:id="age" value="18"onclick="myFunction()"点我id="demo"function myFunction() {var age,voteable;age = document.getElementById("age").value;voteable = (age < 18) ? "太年轻而不能":"年龄够";document.getElementById("demo").innerHTML = voteable + "投票";}