For any other types of variables, it returns "undefined". For example, even if I write something as simple as this:

function() {
var lll = 'abcd'
    return lll
    //return 345
    //return false 
}

The function will return "undefined", in both string and integer cases. But if I return just "false", it works as intended. I tried creating another "javascript code" variable in GTM, doesn't work. I have very little experience with both javascript and GTM so I have no idea what could go wrong.

Update: okay, so now I fixed the strings and integers, the problem was that it wanted a function name (and in the example I was trying to copy, there wasn't one). Now I have another problem - the function outputs undef if I add a line:

var trackers = ga.getAll();

Any ideas?