write subfolder name to array in js

I have a program (for android) and even if my phone comes with a file explorer,
i can't use the <input type="file"> tag so i need to build a file browser.
I already have the var location = "/storage"; variable but i can't read the sub
directories of a folder. i need to write each item to an array, so that i can
display them in <span>` elements.

how would i do that? ps: remember it's for android