<html><body>电子邮件：<input type="email" id="myEmail" placeholder="电子邮件地址"><p>单击该按钮可更改电子邮件字段的占位符文本。</p><button onclick="myFunction()">试一试</button><script>function myFunction() { document.getElementById("myEmail").placeholder = "您的电子邮件地址";}</script></body></html>