<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<body>
<button id="myBn">点我</button>
<p id="demo"></p>
<script>
var x = document.getElementById("myBn");
x.addEventListener("click", myFunction());
function myFunction() {
document.getElementById("demo").innerHTML = 25;
}
</script>
</body>
</html>
哦 知道了,myFunction后加了(),自动执行了
原来x.addEventListener("click", myFunction());
是有这么个限制的啊,学习到了。