<html>
<head> 
<script>
  function validation() {
 var regexp=/^[2-9]{1}[0-9]{3}\s{1}[0-9]{4}\s{1}[0-9]{4}$/;
 			var x=document.getElementById("txtAadhar").value; 
if(regexp.test(x)) {
 window.alert("Your Valid Aadhar no."); 
}
 else 
{ 
window.alert("Invalid Aadhar no."); 
} 
}
</script> 
</head>
 <body>
 <h3>Enter Your Aadhar Number :</h3>
 <input type="text" id="txtAadhar"/></br>
 <input type="button" id="butAadhar" placeholder="Validate Aadhar"  onclick = "validation()" value = "Validate Aadhar"/> 
</body> 
</html>
by