JavaScript runtime error: sEmail' is undefined

Question

I am getting runtime error , please find the code and help me

<script type="text/javascript" src="Scripts/jquery-1.7.1.min.js">

</script>

<script type="text/javascript">

$(document).ready(function () {

$("#txtregUsername").blur(function (e) {

var Username = $("#txtregUsername").val();

if (Username == "" || Username == 0) {

alert("Please valid E-Mail Adress");

debugger;

}

else {

validateEmail(emailID);

}

});

});

function validateEmail(sEmail) {

var filter = /^([\w-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$/;

if (filter.test(sEmail)) {

return true;

}

else {

return false;

}

}

</script>