Dr. McKay

If log on succeeds, you get a loggedOn event. Check the example scripts in the GitHub repo.

You'd want to call logOn for any error event, likely after a delay.

Catch the error event to prevent the crash, and call logOn again to kick off trying to connect.

Not at the moment.

It's not mentioned in the documentation, but you only get an eresult in the error event if a Steam connection can actually be established. If you don't have an eresult proeprty, you can assume there was a network issue.
Only you can properly decide the best course of action for your app, but if your network is down then yeah, probably all you can do is wait and retry until the network comes up.

https://steamerrors.com/5

You can use NetHook2 for this.

If you're using a custom storage engine, don't change the value of the dataDirectory option. If you set it to null, the storage property isn't initialized so you get that error attempting to read 'on' of undefined.
steam-tradeoffer-manager uses the same storage scheme as steam-user, but they don't share the same instance. You need to register your save and read events on your TradeOfferManager instance the same way you registered them on your SteamUser instance.

Decode the JWT and check the exp parameter, but be aware that tokens can be invalidated server-side at Valve's discretion, and nobody's sure exactly what makes that happen besides IP changes.

This is a known issue, see: https://github.com/DoctorMcKay/node-steamcommunity/issues/321
community.login isn't going to work until I can finish the v4 rewrite. Until then, you can either use steam-session or steam-user to get login cookies for use with steamcommunity.

TypeScript definitions for steam-tradeoffer-manager aren't maintained by me, so I can't really help you specifically. That said, you can probably suppress the error using (EResult.Revoked as number)

Don't do it that way, that's a very bad idea. Write the entire 64-bit number to the buffer.

Are you sure? This shouldn't be possible. Steam caches classid+instanceid pairs indefinitely. The description data should never change.
Not really, my best guess is that D just stands for "data". It very likely is a hash to prevent scraping.
It's been my experience that any [SM], A, D triplet will work forever to fetch item data.

Can't be done.

Fixed in 5.0.10

Nevermind, login is done by using refresh token instead of access token lol.

The "Already attempting to log on, cannot log on again" error cannot be caught under any circumstances. If you need to, keep track in your own code if you're already attempting to log on.

steam-session is a Node.js module, not a browser module.

GetTradeHistory does appear to accept an access token to retrieve all trades.

You need to report that you're in CS2 by calling user.gamesPlayed(730), then complete the GC handshaking process before sending any other GC messages. For CS, this is sending ClientHello (4006) with the proper version number and waiting for ClientWelcome (4004) in response.
You can check node-globaloffensive for reference.

I don't believe I've ever seen this happen.

You need to provide the asset owner's SteamID as well. The linked repository only indicates that S is optional because you need either S or M (M is used for market listings).

Not that I'm aware of. I've heard, but not personally confirmed, that if you use an access token you still receive CS2 offers as normal.

You need to call setCookies on the TradeOfferManager instance, not on the SteamCommunity instance. TradeOfferManager's setCookies also retrieves your account's API key.

You'll be fine if you store this in your database.