Make TradeOffer class exportable

I’ve recently stumbled upon the Bluebird library and its’ Promise.promisifyAll method.

It would be cool to have the ability to run

Promise.promisifyAll(require('path-to-trade-offer-manager-class.js'))
Promise.promisifyAll(require('path-to-trade-offer-class.js'))

(or something like that, I didn’t try it yet)

I know I can require('steam-tradeoffer-manager/lib/index.js') to get the TradeOfferManager class, but if I’ll do require('steam-tradeoffer-manager/lib/classes/TradeOffer.js'), it will return an empty object, since this file doesn’t export anything.

So it would be nice to make lib/classes/TradeOffer.js export the TradeOffer function, so I can require just this class and do stuff with it.

[Aareksio]

@autaut03 We’re happy you want to become a part of this open source project and already came with the list of things that are bad/broken in the library. Can’t wait to see more of your contributions. Please make sure you follow the contribution guide while submiting your PR. Here’s a nodejs maintenance chart that may be useful to check which node versions are not depreciated, thus should be supported, please keep them in mind.

I see you have a problem with adding items to trade, filtered by other things than assetid, here is a little snippet you may be interested to use:

const selectedItems = items.filter(item => item.market_name === 'My Item Name');
offer.addItems(selectedItems);

Also, I’ll just leave this, this and perhaps this here for you.

[DoctorMcKay]

@autaut03:

1. I’m incredibly sorry that Steam is slow for you. I would fix that, but last I checked, I don’t work for Valve.
2. Umm, yes? That’s how node’s EventEmitter works.
3. Promises aren’t everything. Node itself doesn’t use promises in its core library, which is why I haven’t prioritized using them here. I don’t use ES6 here because I want to support node v4 (which you say is unnecessary, but it is an LTS version). That’s a breaking change anyway. I’ll add it in the next major version, but I can’t guarantee when that will be. If the code is so bad, why don’t you fix it and send pull requests?
4. You probably think it’s unmodifiable because according to your GitHub profile, you tried to modify it to be a poller for the steamstat.us API. I have no idea why you thought it would be a good idea to rip the polling code out of a completely unrelated and relatively complex project when it’s very easy to write on your own.
5. “Because I don’t personally use it, x functionality is useless.” People do use the real-time trading stuff. If you need to be able to add items by something other than their assetid, Array.prototype.filter may be useful.

@serge1peshcoff I would kind of rather just add promise support manually than use Bluebird, which seems like more of a hack to me. I haven’t reviewed your pull request yet, but I will check it later today. If you’ve done it in a good way then I may be willing to accept it instead of preferring to add promise support manually.