Tryit Editor v1.4

<html>
<head>
<script type="text/javascript">
function validate()
{
var at=document.getElementById("email").value.indexOf("@");
var age=document.getElementById("age").value;
var fname=document.getElementById("fname").value;
submitOK="true";

if (fname.length>10)
 {
 alert("The name may have no more than 10 characters");
 submitOK="false";
 }
if (isNaN(age)||age<1||age>100)
 {
 alert("The age must be a number between 1 and 100");
 submitOK="false";
 }
if (at==-1) 
 {
 alert("Not a valid e-mail!");
 submitOK="false";
 }
if (submitOK=="false")
 {
 return false;
 }
}
</script>
</head>

<body>
<form action="https://w3schools.sinsixx.com/js/tryjs_submitpage.htm" onsubmit="return validate()">
Name (max 10 chararcters): <input type="text" id="fname" size="20"><br />
Age (from 1 to 100): <input type="text" id="age" size="20"><br />
E-mail: <input type="text" id="email" size="20"><br />
<br />
<input type="submit" value="Submit"> 
</form>
</body>

</html>

Your Result:

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