Question Error: cannot send an empty trade offer.

[Kappa]

Hey there, I'm such a newbie in steambot coding. The main objective of the code would be that the bot should request a cs:go / tf2 key from a user who sends the command "!order" via trade offers. My current state is that the bot creates the offer but there's always an error because I get the error: "Cannot send an empty trade offer."

Is there anything which I'm too blind to see?

Thanks in advance!

My code:

 

function checkKeys(steamID) {
	var theirKeys = [];
	var amountOfKeysToAdd = 1;
	manager.getUserInventoryContents(steamID, config.keysFromCSGO && config.keysFromTF2, 2, true, function(err, inventory) {
		if (err) {
			console.log('Error getting user inventory.'.red);
		} else {
			console.log('Checking if user has CS:GO or TF2 keys.'.green);
			for (var n = 0; n < inventory.length; n++) {
				if(theirKeys.length < amountOfKeysToAdd && config.acceptedKeys.indexOf(inventory[n].market_hash_name) >= 0) {
					theirKeys.push(inventory[n]);
					console.log(inventory[n].market_hash_name);
				}
			}
			console.log('User has' + theirKeys.length + 'key(s).');
		}
	});
}

function sendOffer(sender) {
let theirKeys = [];
var offer = (manager.createOffer(sender.getSteamID64()));
	offer.addTheirItems(theirKeys);
	offer.send ((err, status) => {
		if (err) {
			console.log('There was an error sending the offer.'.red + err);
		} else {
			console.log('An offer has been sent.'.green);
			console.log(status);
		}
	});
}

client.on('friendMessage', (sender, message) => {
	if (message === "!start") {
		client.chatMessage(sender, config.startMessage);
	} else if (message === "!owner") {
		client.chatMessage(sender, config.ownerMessage);
	} else if (message === "!help") {
		client.chatMessage(sender, config.helpMessage);
	} else if (message === "!order") {
		client.chatMessage(sender, config.orderMessage);
		client.chatMessage(sender, 'Processing your request....');
		checkKeys(sender);
			console.log('Creating offer...'.cyan);
			sendOffer(sender);
	} else if (message === "!proof") {
		client.chatMessage(sender, config.proofMessage);
	}
});

 

[Dr. McKay]

You need to research how asynchronous code works in JavaScript.

[Kappa]

Even though with some help I've managed to get my code work, you're definetly right. Thanks anyways!