mobile.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Moblie number validation</title>
  </head>
  <body>
    <form>
      <input id="text1" placeholder="Enter Moblie Number" type="text" />
      <label id="lbl1text" style="color: red; visibility: hidden">Invalid</label
      ><br />
      <button onclick="validate()" type="button">Validate</button>
    </form>

    <script>
      function validate() {
        let text = document.getElementById("text1").value;
        let regex = /^[6-9]\d{9}$/;

        if (regex.test(text)) {
          document.getElementById("lbl1text").innerHTML = "Valid";
          document.getElementById("lbl1text").style.visibility = "Visible";
          document.getElementById("lbl1text").style.color = "green";
        } else {
          document.getElementById("lbl1text").innerHTML = "Invalid";
          document.getElementById("lbl1text").style.visibility = "Visible";
          document.getElementById("lbl1text").style.color = "red";
        }
      }
    </script>
  </body>
</html>