WordPress open all external links in new window.

open_external_links_in_new_window.php

<?php
function sjaved_open_external_links_in_new_window(){ ?>
    <script type="text/javascript">
    jQuery(document).ready(function($){
        $('a').each(function() {
           var a = new RegExp('/' + window.location.host + '/');
           if(!a.test(this.href)) {
               $(this).click(function(event) {
                   event.preventDefault();
                   event.stopPropagation();
                   window.open(this.href, '_blank');
               });
           }
        });
    });
</script>
<?php }
add_action('wp_footer', 'sjaved_open_external_links_in_new_window', 100);