为什么此代码只给我默认值
<!DOCTYPE html>
<html>
<body>
<p id= "demo"></p>
<input id="age" />
<button onclick="document.getElementById('demo').innerHTML=text">try it</button>
<script>
var text;
age = document.getElementById('age').value;
switch (age) {
case 10:
text = "diuble";
break;
case 13:
text = "puberty";
break;
case 18:
text = "Beer!";
break;
default:
text = "Looking forward to the Weekend";
}
</script>
</body>
</html>
我曾尝试将document.getElementById（'age'）。value更改为18，当我这样做时，它的输出为啤酒！但现在它只给了我期待。...
您没有调用函数onclick，而是在加载文档时触发了代码。正确的方法是：
function getText(){
var text;
age = document.getElementById('age').value;
age = parseInt(age)
switch (age) {
case 10:
text = "diuble";
break;
case 13:
text = "puberty";
break;
case 18:
text = "Beer!";
break;
default:
text = "Looking forward to the Weekend";
}
document.getElementById('demo').innerHTML=text
}<p id= "demo"></p>
<input id="age" />
<button onclick="getText()">try it</button>