<!DOCTYPE html>
<html>
<body>
电子邮件：<input type="email" id="myEmail">
<p>单击该按钮可设置电子邮件字段的宽度。</p>
<button onclick="myFunction()">试一试</button>
<script>
function myFunction() {
document.getElementById("myEmail").size = "50";
}
</script>
</body>
</html>