npm and error messages

node_modules/core-js/modules/_string-context.js

@@ -0,0 +1,8 @@
+// helper for String#{startsWith, endsWith, includes}
+var isRegExp = require('./_is-regexp');
+var defined = require('./_defined');
+
+module.exports = function (that, searchString, NAME) {
+  if (isRegExp(searchString)) throw TypeError('String#' + NAME + " doesn't accept regex!");
+  return String(defined(that));
+};