Automatically open external links in new tab or window.

_blank.js

// vanilla JavaScript
var links = document.links;

for (var i = 0, linksLength = links.length; i < linksLength; i++) {
  if (links[i].hostname != window.location.hostname) {
    links[i].target = '_blank';
  } 
}

// or in jQuery
$(document.links).filter(function() {
  return this.hostname != window.location.hostname;
}).attr('target', '_blank');