2010 forms - is there a way to autocomplete a text field

only with a javascript.

have a look on this thread -  

Thanks Marian. Is there a non-repeating section example?

And I don't want to reference a sharepoint list, just the cache. 

read through the thread I posted, there is a link to another page that provides solution for simple text control out of repeating section.

you need not to take source items from a remote list, you can define your own array variable, like

var cache=["option1","option2","option3"];‍