To answer this,
As the at(index) method is in the proposal now and not added to the JavaScript language yet, we can only use it with the help of a Polyfill.
As the Polyfil I am using is available as an NPM, I have installed it and imported it for using the at() method.
The beauty of it is, if there is support of it in JavaScript language in the future, you can just remove that import from the code along with the polyfill entry from the package.json file. That's it.
I have mentioned the polyfill above under the section, "The at(index) method is Brand New".
Thanks a lot for asking and discussing.