JavaScript Redirect Code

A JavaScript redirect changes window.location from client-side script, which is useful when the destination depends on something only the browser knows — a condition checked after page load, a value read from localStorage, a redirect fired from inside an event handler. It runs after the page has already loaded and parsed, so it is always slower than a server-side redirect and should not be the first choice for a permanent page move that search engines need to understand.

location.href vs location.replace — the difference that matters

window.location.href = url navigates to the new page and adds a history entry, so pressing back returns to the redirect page — which immediately fires again, trapping the visitor in a forward-back loop. window.location.replace(url) overwrites the current history entry instead of adding a new one, so back skips straight past the redirect page to wherever the visitor was before it.

replace() is almost always what you actually want for a redirect. Reach for href only in the rare case where you deliberately want the redirect page to remain in the browser history.