What you’re seeing is the console showing you what it is that you are returning - it’s not to do with using map or filter. console.log(JSON.stringify(filteredList)) is generally very useful when logging objects so you see a string representation. Note this is what appears in my console, most browsers should allow you to inspect what each object is in detail:
It’s very useful for logging stuff so you can quickly see what you’re looking at - the non-stringified version is normally more useful, as you can drill into the object in the console, but to just see straightaway what is coming back, stringify is invaluable