Check if links are external with jQuery/javascript?
<script type="text/javascript">
var comp = new RegExp(location.hostname);
jQuery('a').each(function(){
//location.hostname === this.hostname || !this.hostname.length
if(comp.test(jQuery(this).attr('href'))){
// a link that contains the current host
jQuery(this).addClass('local');
}
else{
// a link that does not contain the current host
jQuery(this).attr('rel','nofollow');
}
});
</script>