Most expected behavior for invisible typeahed in a list

I have a long list of functions (around 25) and I would like to build a typeahead feature for it. When you press D the selection should jump to the first entry that starts with an D (for Excel it is DATE).


  • What happens if I type an ‘A’ as the next character? Does it stay at ‘DATE’ or jump to the first entry with ‘A’?
  • If the system saves more than one character (‘DA’) when does it erase its memory and the user can start fresh? 200ms, 500ms?

What would you expect?

This is a screenshot from Excel, my interface looks similar.

excel formulas