<html>
<body>
<form action="form_action.asp">
主页: <input type="url" id="myURL" name="website" required>
<input type="submit">
</form>
<p>点击 "点我" 按钮查看在表单提交前URL字段是否为必填字段。</p>
<button onclick="myFunction()">点我</button>
<p id="demo"></p>
<script>
function myFunction() {
var x = document.getElementById("myURL").required;
document.getElementById("demo").innerHTML = x;
}
</script>
</body>
</html>