LinksHighlight.js

function linkHighlight() {
	let colors = {
		"HostBg":  	"#00F", "Host":  	"#FFF", "HostOut":  	"#000",
		"DomainBg":	"#808", "Domain":	"#FFF", "DomainOut":	"#000",
		"OtherBg": 	"#F00", "Other": 	"#FFF", "OtherOut": 	"#000",
		"WikiBg":  	"#FF0", "Wiki":  	"#000", "WikiOut":  	"#000",
	};

	let Hosts     	= {};
	let Domains   	= {};
	let pageHost  	= location.hostname
	let pageDomain	= pageHost.split(".").slice(-2).join(".");
	let index     	= 0;

	for ( ; link = document.links[index] ; ++index ) {
		let linkHost   = link.hostname;
		let linkDomain = linkHost.split(".").slice(-2).join(".");

		  Hosts.hasOwnProperty( linkHost   ) ?   Hosts[ linkHost   ]++ :   Hosts[ linkHost   ] = 1;
		Domains.hasOwnProperty( linkDomain ) ? Domains[ linkDomain ]++ : Domains[ linkDomain ] = 1;

		                                               let color = "Other";
		if ( pageDomain === linkDomain             ) {     color = "Domain";  }
		if ( pageHost   === linkHost               ) {     color = "Host";    }
		if ( linkDomain.indexOf("wikipedia.") == 0 ) {     color = "Wiki";    }

		link.target = "_blank";
		link.style.color           = colors[color];
		link.style.backgroundColor = colors[color + "Bg"];
		link.style.outlineColor    = colors[color + "Out"];
	}

	let message = "LinkHighlight: Found " + Object.keys(Domains).length +" domains and " + Object.keys(Hosts).length + " hosts in " + index + " links.";

	console.groupCollapsed( message );
		console.groupCollapsed( 'Domains' );
			console.table(Domains);
			console.groupEnd();
		console.groupCollapsed( 'Hosts' );
			console.table(Hosts);
			console.groupEnd();
		console.groupEnd();

	alert( message );

	return true;
}

linkHighlight();