https://www.alphadictionary.com/js/external.js

1/*
2        external.js - standards-compliant way of opening new-window links
3		$Id: external.js,v 1.1 2004/11/16 22:27:49 ashaffer Exp $
4        $Revision: 1.1 $
5		From http://www.sitepoint.com/article/standards-compliant-world/3
6*/
7(function() {
8    function externalLinks() {
9	if (!document.getElementsByTagName) return;
10	var anchors = document.getElementsByTagName("a");
11	for (var i=0; i<anchors.length; i++) {
12	    var anchor = anchors[i];
13	    if (anchor.getAttribute("href") &&
14		(anchor.getAttribute("rel") != null) && 
15		(anchor.getAttribute("rel").indexOf("external") !== -1)) {
16		anchor.target = "_blank";
17	    }
18	}
19	var forms = document.getElementsByTagName("form");
20	for(var i = 0; i<forms.length; i++) {
21	    var form = forms[i];
22	    /* Abuse of the class attribute. */
23	    if(form.getAttribute("class") == "external") {
24		form.target = "_blank";
25	    }
26	}
27    }
28    
29    var exchainonload = window.onload;
30    window.onload = function() {externalLinks(); if(exchainonload) exchainonload();}
31})();