Firefox

It can be formatted "nicely" with no issue. But that doesn't necessarily make it easy to understand.

What that person posted was in a function named smb() that only gets called by rmb() under certain conditions, and rmb() gets called by AdB() under other conditions after being called from eeB() used in BaP().... it's a long list of hard to read minified functions and variables in a mess of chained calls, declared in an order that doesn't necessarily match up with what you'd expect would be the flow.

In the same file you can also easily find references to the user agent being read at multiple points, sometimes storing it in variables with equally esoteric short names that might sneak past the reader if they aren't pedantic enough.

Like, for example, there's this function:

function vc() {
    var a = za.navigator;
    return a && (a = a.userAgent) ? a : ""
}

Searching for vc() gives you 56 instances in that file, often compared to some strings to check what browser the user is using. And that's just one of the methods where the userAgent is obtained, there's also a yc=Yba?Yba.userAgentData||null:null; later on too... and several direct uses of both userAgent and userAgentData.

And I'm not saying that the particular instance that was pointed out was the cause of the problem.. it's entirely possible that the issue is somewhere else... but my point is that you cannot point to a snippet of "nicely formated" messed up transpiler output without really understanding fully when does it get called and expect to draw accurate conclusions from it.