Copying here the discussion held in dev chat so other users can see it:
David Mudrák:
Mustache uses JSONable data so basically two supported data structures are:
* lists (in PHP speak, numeric arrays that _must_ have sequential indexes), or
* dictionaries/hashes (in PHP speak, associative arrays or objects)
Common problem is when trying to work with numerical arrays with non-sequential indexes, such as results of get_records()
Igor Sazonov:
Hi, David! yes, i understand about sequal in indexes in numerical arrays, for example, i have array item like `$item[0][0][0]`, so in Mobile mustache template i cant dispay it. I mean not web-based mustache but Mobile with `<% %>` tags from here https://docs.moodle.org/dev/Mobile_support_for_plugins
or array item like $item[0][0]['associative'] and nother kinds)
David Mudrák:
Correct. As far as I know, there is no way in Mustache to address list items. Only iterate through them.
So if you pass it a list of items, there is no way in Mustache to display the first one and stop.
Things like {{a.0}} only work in some implementations as side effects
Igor Sazonov:
Then I don't understand how to fetch a key in array loop)
David Mudrák:
You can't. You have to pass it is a list of objects with like "index" and "value" properties.
[{ix: 1, val: 'Foo'}, {ix: 2, val: 'Bar'}]
Igor Sazonov:
Yes, I know, I did that) but it works only for simple arrays, not multidimensional
David Mudrák:
Well, "value" can be another list, no?
It is a bit counter-intuitive if you are used to PHP structures, I know.