<html>
<body>
<p>文档添加 onmousemove 事件句柄，当在文档中移动鼠标时会显示随机数。</p>
<p>点击按钮移除事件句柄。</p>
<button onclick="removeHandler()">点我</button>
<p id="demo"></p>
<script>
document.addEventListener("mousemove", myFunction);
function myFunction() {
document.getElementById("demo").innerHTML = Math.random();
}
function removeHandler() {
document.removeEventListener("mousemove", myFunction);
}
</script>
</body>
</html>