<!DOCTYPE html>
<html>
<body>
<h1>button popovertargetaction 属性</h1>
<h1 popover id="myheader">Hello</h1>
<button popovertarget="myheader" popovertargetaction="show">显示弹出框</button>
<p>单击该按钮，将显示弹出框元素。</p>
</body>
</html>