<!DOCTYPE html>charset="utf-8"W3Cschool教程(w3cschool.cn)点击按钮检测年龄。年龄: id="age" value="18"是否达到投票年龄?onclick="myFunction()"点击按钮id="demo"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;}