Both approaches can be sourced from a Webflow Collection List.
HTML5's <datalist> approach;
jQuery's autocomplete;
DEMO
Below are two variations on text INPUT autocomplete. The first uses HTML5's <datalist>, and the second uses jQuery's autocomplete.
Type into either of the lists to see autocomplete in action. Both use the same source list.
See the designer view of this demonstration by clicking the button at the top.
Then view this part of the layout for details;
Coming soon.