Validate Email - Javascript

<script  type="text/javascript"> 

//Function to validate Email 

function  IsValidEmail(email) {

//var exclude=/[^@\\-\\.\\w]|^[_@\\.\\-]|[\\._\\-]{2}|[@\\.]{2}|(@)[^@]*\\1/; 

var  exclude = /[^@\\-\\.\\w]|^[_@\\.\\]|[\\._\\-]{2}|[@\\.]{2}|(@)[^@]*\\1/;

var  checkend = /\\.[a-zA-Z]{2,3}$/;

if  ((email.search(exclude) != -1) || (email.search(checkend) == -1)) {

return  false ;

}

atPos = email.indexOf("@" , 0);

pPos1 = email.indexOf("." , 0);

periodPos = email.indexOf("." , atPos);

pos1 = pPos1;

pos2 = 0;

while  (pos2 > -1) {

pos2 = email.indexOf("." , pos1 + 1);

if  (pos2 == pos1 + 1) {

return  false ;

} else  {

pos1 = pos2;

}

}

if  (atPos == -1) {

return  false ;

}

if  (atPos == 0) {

return  false ;

}

if  (pPos1 == 0) {

return  false ;

}

if  (email.indexOf("@" , atPos + 1) > -1) {

return  false ;

}

if  (periodPos == -1) {

return  false ;

}

if  (atPos + 1 == periodPos) {

return  false ;

}

if  (periodPos + 3 > email.length) {

return  false ;

}

return  true ;

}

</script>