support.html

<!doctype html>
<html lang="en">

<head>
  <title>Support Chat</title>
  <!--Link to CSS -->

  <link href="./css/sign.css" rel="stylesheet">
</head>

<body class="text-center">
    <div class="center">

   
        <h1 >Chat Supporter</h2>
  <form class="form-signin" id="frm"  >
    <div class="content">
        <input type="text" id="email" name="email" class="form-control"  required> </input>
        <span></span>
        <label for="email">Email</label>
  
    </div>
    <button class="btn" value="submit" id="myButton"  >Start Chat</button>
  </form>
 
</div>
</body>

</html>

<script type="text/javascript">
    document.getElementById("myButton").onclick = function () {
      const regEx = /[a-zA-Z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,8}(.[a-z{2,8}])?/g;
      if(regEx.test(document.getElementById("email").value)){
        document.getElementById("frm").action="chat.html";

      }else{
        alert("Invalid Email");
      }

    

}
document.getElementById("frm").onsubmit = function () {
        const regEx = /[a-zA-Z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,8}(.[a-z{2,8}])?/g;
      if(regEx.test(document.getElementById("email").value)){
    
        document.getElementById("frm").action="chat.html";
      }else{
        alert("Invalid Email");
      }
      }
     
   
</script>