ehhh. Only if your API is incredibly simple. You still have to roughly know that some operation exists and what that likely name is for the operation. Otherwise you're scrolling through a list of hundreds or even thousands of possible matches.
If you know you have an array and you know what you want to do with that array but don't know the name of the operation you want to do with that array, then completion as a form of discover sucks. No one is likely to stumble upon, say, JS's ".some()" method without having prior knowledge that this function exists and have it do exactly what they want.
Yes, you still have to know kind of how it was named and kind of how it was used. It is just the rest of the details you can forget (or likewise, don't need to remember). It is really useful when you have to use libraries that are kind of similar but not exactly.
Anecdotally, I use Typescript and code completion is exactly how I discovered Javascript's "some" and "every" methods. It involved lots of scrolling because I didn't know it would be named like that, but based on the presence of other list comprehension methods I had a good suspicion that they were there somewhere...I still often mistakenly write LINQ-named "all" and "any", but the online type checking quickly snaps me out of it. Code completion can actually be improved to deal with these cases with more utility, by not only matching on the parts of the member's name, but a system could also match on synonyms to parts of what you typed as well (or document aka's in the interface that play no other role than hooking into code completion).
Nobody is suggestion autocomplete replaces basic API knowledge, reading the docs, etc. What they’re saying is autocomplete saves having to remember every facet of the API precisely.
It’s like a rounded edge on plug pins, you still have to know where the plug socket is to plug something in but the rounded pins mean You don’t need to be millimetre perfect when inserting it because the plug will slide along the curve and guide itself into the socket.
That’s the point of autocomplete, it’s about enabling developers to focus on remembering the important stuff while the IDE helps guide them around the more granular bits that are still syntactically important to the compilation of software but don’t really matter to the logic you’re writing.
Code completion does replace a lot of doc use cases, like autocomplete in a shell reduces the need to go to man pages. But ya, code and auto completions are like HUDs for more structured experiences based around text editing.
If you know you have an array and you know what you want to do with that array but don't know the name of the operation you want to do with that array, then completion as a form of discover sucks. No one is likely to stumble upon, say, JS's ".some()" method without having prior knowledge that this function exists and have it do exactly what they want.