如何在未填寫輸入時顯示錯誤消息？這是我的代碼：<body>
<form method="post">
<label>Enter your name</label>
<input id="myName" type="text" placeholder="Your name here"><br>
<label>enter your first name</label>
<input id="myFirstName" type="text" placeholder="Your first name here"><br>
<input id="myButton" type="button" value="submit">
</form>
<p id="mydisplay"></p>
<script src="script.js"></script></body>function myFunction(){
var x = document.getElementById("myName").value + "<BR>" + document.getElementById("myFirtName").value ;
if (x != ""){
alert("Thank you fill in the fields")
} else{
document.getElementById("myDisplay").innerHTML = x;
}}window.addEventListener("click", function () {
document.getElementById("myButton").addEventListener("click", myFunction);});但我之前測試了字段，但沒有顯示錯誤消息告訴我輸入為空。另一方面，它顯示了我在我的頁面輸入中標記的內(nèi)容
如何在javascript中填寫字段時顯示錯誤消息？
暮色呼如
2019-04-26 18:15:58