How do I detect the raw user input typed into a browser's address bar?

The browser address bar on modern browsers support not only the GET request for URL inputs, but can also invoke a search result POST request(according to their default search engine) if the input is not a URL.

I'm trying to obtain this raw user input before it turns into a search request.

I don't believe my question is answered by this (almost) similar question: How can I detect an address bar change with JavaScript? which looks to detect the hash change in-between site changes.

How do I detect the raw user input typed into a browser's address bar?