emailVal.html

<html>
    <head>
        <script type="text/javascript">
        
        function fun(){
var a=document.getElementById("inp").value;
var b=/^([a-zA-Z0-9\.-]+)@([a-zA-Z0-9-]+).([a-zA-Z]{2,10})(.[a-zA-Z]{2,8})?$/;

if(b.test(a)){
    document.getElementById("lab").innerHTML="valid";

document.getElementById("lab").style.visibility="visible";
document.getElementById("lab").style.color="green";


}
else{
    document.getElementById("lab").innerHTML="Invalid";

document.getElementById("lab").style.visibility="visible";
document.getElementById("lab").style.color="red";


}
        }
        
        </script>
    </head>

<body>

<form>

<input id="inp" placeholder="enter_Name">
<label id="lab" style="color: red;visibility:hidden">Invalid</label>
<button onclick="fun()" type="button">click me</button>


</form>


</body>


</html>