So siehts ganz gut aus !

node_modules/es5-ext/function/#/copy.js

@@ -0,0 +1,23 @@
+"use strict";
+
+var mixin         = require("../../object/mixin")
+  , validFunction = require("../valid-function")
+  , re            = /^\s*function\s*([\0-')-\uffff]+)*\s*\(([\0-(*-\uffff]*)\)\s*\{/;
+
+module.exports = function () {
+	var match = String(validFunction(this)).match(re), fn;
+
+	// eslint-disable-next-line no-new-func
+	fn = new Function(
+		"fn",
+		"return function " +
+			match[1].trim() +
+			"(" +
+			match[2] +
+			") { return fn.apply(this, arguments); };"
+	)(this);
+	try {
+		mixin(fn, this);
+	} catch (ignore) {}
+	return fn;
+};