Typekit fonts for TinyMCE editor plugin

typekit.editor.php

add_filter("mce_external_plugins", "tomjn_mce_external_plugins");
function tomjn_mce_external_plugins($plugin_array){
	$plugin_array['typekit']  =  get_template_directory_uri().'/typekit.tinymce.js';
    return $plugin_array;
}

typekit.tinymce.js

(function() {
	tinymce.create('tinymce.plugins.typekit', {
		init: function(ed, url) {
			ed.onPreInit.add(function(ed) {

				// Get the DOM document object for the IFRAME
				var doc = ed.getDoc();

				// Create the script we will add to the header asynchronously
				var jscript = "(function() {\n\
					var config = {\n\
						kitId: 'xxxxxxx'\n\
					};\n\
					var d = false;\n\
					var tk = document.createElement('script');\n\
					tk.src = '//use.typekit.net/' + config.kitId + '.js';\n\
					tk.type = 'text/javascript';\n\
					tk.async = 'true';\n\
					tk.onload = tk.onreadystatechange = function() {\n\
						var rs = this.readyState;\n\
						if (d || rs && rs != 'complete' && rs != 'loaded') return;\n\
						d = true;\n\
						try { Typekit.load(config); } catch (e) {}\n\
					};\n\
					var s = document.getElementsByTagName('script')[0];\n\
					s.parentNode.insertBefore(tk, s);\n\
				})();";

				// Create a script element and insert the TypeKit code into it
				var script = doc.createElement("script");
				script.type = "text/javascript";
				script.appendChild(doc.createTextNode(jscript));

				// Add the script to the header
				doc.getElementsByTagName('head')[0].appendChild(script);

			});

		},
		getInfo: function() {
			return {
				longname: 'TypeKit For TinyMCE',
				author: 'Tom J Nowell',
				authorurl: 'http://tomjn.com/',
				infourl: 'http://twitter.com/tarendai',
				version: "1.1"
			};
		}
	});
	tinymce.PluginManager.add('typekit', tinymce.plugins.typekit);
})();

Thanks man @NeilJS

Also huge thanks to Tom Nowell for getting this going in the first place.

TinyMCE has since deprecated the onPreInit function in version 4.x, which WordPress now uses. It doesn't cause any errors, in fact it still works, but there is a log in the console stating that it is deprecated (giving no optimal solution, leaving it to me to save the day).

Replacing line 4 in typekit.tinymce.js with this will ensure future compatibility:

            ed.on('PreInit', function(e) {

Documentation on the on('PreInit') function is here.