kartik-v/bootstrap-fileinput - load file with JavaScript rather then with window.FileReader

Today I'm having one he11 of a question. Hope you gonna enjoy it, coz I'm trying to find a solution for this one for about 3 days now. So here how it states:

I'm using kartik-v/bootstrap-fileinput. And I'm trying to pull out a curtain effect here. I want to make it look like something is already selected upon a specific event (let's say - upon loading the page). I've found a "previewFile" (line 1175) method there in a FileInput.prototype describtion (line 255) which is in fileinput.js, not so sure how do I use it in a way that gonna suit my needs.

So let's summarize: upon loading a document I'd like this fileinput to have already something selected, and yeah I know that you cannot set a dynamically set, just make it feel like something is already selected.

Thx for any help!

p.s.: if ya want me to upload some example can do it tomorrow: it's just that it is 8 pm and i wanna go home from mah work.