So siehts ganz gut aus !

node_modules/es5-ext/array/#/copy-within/is-implemented.js

@@ -0,0 +1,7 @@
+"use strict";
+
+module.exports = function () {
+	var arr = [1, 2, 3, 4, 5];
+	if (typeof arr.copyWithin !== "function") return false;
+	return String(arr.copyWithin(1, 3)) === "1,4,5,4,5";
+};