TomYoki

Unfortunately not. I might have worked on reverse-engineering the Source protocol to join a game server, but to join any useful server you'd have to implement VAC which is just insane enough that I'm not touching it.

You would probably want to do something like this:
Initialize a variable to 0 to count the user's owned metal Loop over the user's inventory, and add 9 to that variable for every refined, 3 for every reclaimed, and 1 for every scrap If that variable is If it's >=, then loop over their inventory again, starting with refined and add ref until they don't have any more or the amount you need Keep going with rec and eventually scrap If, at the end, you're short a bit, add the smallest currency unit to go above your required price

You're probably running out of memory.

`amount` property is your friend.
https://github.com/DoctorMcKay/node-steamcommunity/wiki/CEconItem#amount

Sorry about that, update to 3.35.1 and it should be good to go.

Honestly, don't comment if you have absolutely no clue what's going on.
 
 
This should work:
 
EDIT: You also have 3 other issues with your code that I did not notice at first (as I didn't look at the main code).
1.) You are using a deprecated method. You want to use https://github.com/DoctorMcKay/node-steam-tradeoffer-manager/wiki/TradeOfferManager#getinventorycontentsappid-contextid-tradableonly-callback
Example: 
manager.getUserInventoryContents(partner, appid, contextid, true, (err, theirInv) => {...}); 2.)  Line 158 it needs to be either 'var', 'let' or 'const' unless you are wanting to re-define it.
 
3.)  last issue (that I found) would be on line 163, what you want to do there is change it to 
var keyToAdd = availableKey[0] //Change it simply to 'availableKey' if you want to add all of the keys found. and from there refer to it as keyToAdd.
 
 
 
Back to your solution for 'checkAvailableKey' function
function checkAvailableKey(inventory, acceptedKeyList){ var availableKey = []; //Create an empty array where we can store item data. for(var i=0; inventory.length>i;i++){ //Loop through inventory. if (acceptedKeyList.indexOf(inventory[i].market_hash_name) >= 0){ //Check if there is this item in your array. availableKey.push(inventory[i]); //Push all item info, such as assetid, name, amount etc. } } return availableKey; //return the array with item data. /* P.S: You don't need to make the function ask for the array every time, just add the array with accepted keys in your global scope. However, this is prefered if you have multiple arrays which you want to check. */ }

While we're on this topic, are you planning on adding these features to node-steamcommunity, and something like a feature to get Group comments, as a lot of people are wanting to make a bot that can remove people spamming "Come to this awesomesite.csgo/getScammed.php for free moneeeeeys!!1" .

just call 
manager.getExchangeDetails(); https://github.com/DoctorMcKay/node-steam-tradeoffer-manager/wiki/TradeOffer#getexchangedetailsgetdetailsiffailed-callback

Are you wanting to cancel existing offers after X time has passed?
 
If so, have a look at constructor options: https://github.com/DoctorMcKay/node-steam-tradeoffer-manager/wiki/TradeOfferManager-@-v1#constructoroptions

You'd need to retrieve the TradeOffer object using getOffer or getOffers then call cancel() on that object.

The npm name is just steamcommunity.

offer.itemsToReceive.forEach(function(item) { if (item.appid == "440" && item.market_hash_name == "Scrap Metal") { console.log("It's a bird! It's a plane! IT'S A SCRAP METAL!"); } } ); Something I made you real quick. 
You can do it the same way for itemsToGive
 
You can also get some of this info out of it:
https://github.com/DoctorMcKay/node-steamcommunity/wiki/CEconItem

You can use "split" to convert the string to array and get the part you want. Example:
client.on('friendOrChatMessage', (senderID, message) => { //Example Message: /bet 45 var arrmsg = message.split(" ") //arrmsg = ["/bet","45"] var userNumber = arrmsg[1] if (message.indexOf("/bet") == 0){ client.chatMessage(senderID, 'Your bet is: ' + userNumber); } });

You should use a loop (for, foreach, while, etc) to iterate all the inventory callback, you can create an array called items, and in each iteration you push a object like this one:
var item = { "assetid": inventory[i].id, "name": inventory[i].market_hash_name } if you need to make an asynchronous operation with that info and know when all iterations are finished, you can use async module. 

The easiest way to determine which game a community item belongs to is to check its market_hash_name. All cards/emoticons/backgrounds have their market_hash_names prefixed with the game's appid and a hyphen (e.g. "440-SCOUT").