<html>
<body>
<p>该实例使用 addEventListener() 方法来向按钮添加点击事件。</p>
<button id="myBtn">点我</button>
<p id="demo"></p>
<script>
document.getElementById("myBtn").addEventListener("click", function(){
document.getElementById("demo").innerHTML = "Hello World";
});
</script>
</body>
</html>