Sorry for the delay. I don't have a suggestion, but I could help you find a solution.
Do you have a list or database for your autocomplete?
How long is your list? Is it an open-end list?
Javscript is fast enough, as has been suggested.
If you google
javascript autocomplete, there are plenty of answers.
It appears JquerUI has auto complete.
https://jqueryui.com/autocomplete/Jesse