npm and error messages

node_modules/es6-weak-map/is-native-implemented.js

@@ -0,0 +1,8 @@
+// Exports true if environment provides native `WeakMap` implementation, whatever that is.
+
+'use strict';
+
+module.exports = (function () {
+	if (typeof WeakMap !== 'function') return false;
+	return (Object.prototype.toString.call(new WeakMap()) === '[object WeakMap]');
+}());