Untitled

<!DOCTYPE html>
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>JSP Page</title>
    <script src="newjavascript.js"></script>
  </head>
   <body>
 Name:         <input type="text" value="" id="t1"><br>
 Age:          <input type="text" value="" id="t2"><br>
 Rollno:       <input type="text" value="" id="t3"><br>
 Address:      <input type="text" value="" id="t4"><br>
<div id="er" style="color: red;"></div>
<input type="submit" value="Submit" onclick="validation()">
 </body>
</html>

var st_roll_no="";

function validation()
{
if (document.getElementById("t1").value.replace(/^s+|s+$/g, "") === "")
{
    document.getElementById("er").innerHTML = "please select name";
}
else if (document.getElementById("t2").value.replace(/^s+|s+$/g, "") === "")
{
    document.getElementById("er").innerHTML = "please select age";
}
    else if (document.getElementById("t3").value.replace(/^s+|s+$/g, "") != "")
{
    fetch_rollno(document.getElementById("t3").value);
            alert("After fetching the result is "+st_roll_no);
}
      else if (st_roll_no.replace(/^s+|s+$/g, "") === "found")
{
    document.getElementById("er").innerHTML = "Please enter address";
}
   else if (document.getElementById("t4").value.replace(/^s+|s+$/g, "") === "")
{
    document.getElementById("er").innerHTML = "Please enter address";
}
    else
    {
        alert("success");
    }
}

function fetch_rollno(rollno)
 {
 $.ajax({
            type: "POST",
            url: 'validate_rollno',
            data: {rollno: rollno},
            success: function(result)
            {
                alert("result from database is "+result);
            if (result == "found")
                {
                    alert("if");
                    st_roll_no="found";
                    alert(st_roll_no);

                }
                else
                {
                     alert("else");
                     st_roll_no="notfound";
                     alert(st_roll_no);

                }

            }
        });
    }

alert("After fetching the result is "+st_roll_no);