You can’t reliably “save & restore” an entire site purely with client-side JavaScript — browsers won’t let JS fetch arbitrary archived assets and rewrite every link for a full site restore. A practical approach is to pull the archived HTML and assets from the Wayback Machine (or use an automated tool like www.waybackdownloader.com) and then serve the downloaded files (fix relative links, update absolute URLs, restore assets, and test). If you want to prototype with JS, fetch archived HTML via the Wayback API, rewrite asset URLs to point to your downloaded copies (or to archive URLs), and then inject the page — but for complete restoration, an automated downloader + a short post-processing step is far more reliable.