adma

Next time, please present properly formatted code with curly braces... its very disorientating to follow if .. else statements that do not use curly brackets...

I don't know what you are trying to do with the comma operator, but by the looks of it you want to use the and operator (&&) in your if (onlyKeys, onlyRef) checks...
 
if (onlyKeys2, onlyRef2) âž¡ if (onlyKeys2 && onlyRef2)
 
In regards to your declining offer thing... its probably to do with your lack of curly braces surrounding if and else e.g
if (x && y) { // code } else { // code } Not ...
if (x && y) // code else // code What do these lines do/mean?
'refAmount = offer.itemsToGive.length == keyAmount * buyprice'
'refAmount = offer.itemsToReceive.length == keyAmount * sellprice'
 
Also, unless you want the refAmount and keyAmount to be global, you should really declare them with var ... keyAmount = offer.itemsToGive.length âž¡ var keyAmount =  offer.itemsToGive.length
 
Even though I am new to coding/scripting and I can see your code is very untidy/messy...
 
PS: What is offers.on('newOffer') ? and why is trade offer manager newOffer listener nested inside this???

manager.on("newOffer", function(offer) {
var onlyKeys = (offer.itemsToReceive.every(function(item) {
return item.name == "Mann Co. Supply Crate Key";
}));

if (onlyKeys) {
keyAmount = offer.itemsToReceive.length
console.log("Received trade offer containing " + keyAmount + " keys, accepting");
offer.accept(function(err) {
if (err) console.log(err);
});
} else {
console.log("Trade offer contains non key items. Declining");
offer.decline(function(err) {
if (err) console.log(err);
});
}
} 

If you want to get the market hash names of each item you're giving, you would probably use forEach or a for loop to cycle through the itemsToGive array ...
e.g
manager.on('newOffer', function(offer) { offer.itemsToGive.forEach(function(item) { console.log("Item to give : " + item.market_hash_name); // Items to give: Chroma 2 Case }); }); a for ... of loop (edited from for..in loop)
manager.on('newOffer', function(offer) { for (var item of offer.itemsToGive) { console.log("Items to give : " + item.market_hash_name); // Items to give: Chroma 2 Case } }); a regular for loop
manager.on('newOffer', function(offer) { for (var i = 0; i < offer.itemsToGive.length; i++) { console.log("Items to give #" + i + " : " + offer.itemsToGive[i].market_hash_name); // Items to give #1 : Chroma 2 Case } });Same deal will apply for itemsToReceive ... or any other array you wanted to cycle through
 
read here https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Loops_and_iteration

Check fromRealTimeTrade and abort if it's true in newOffer.

https://github.com/DoctorMcKay/node-steam-tradeoffer-manager/wiki/Real-Time-Trades

I honestly can't believe how prompt you were with implementing this. Thanks very much McKay!