SteamID64

[TextDynasty]

ERROR

"uri": "https://steamcommunity.com/inventory/" + userID.
getSteamID64() + "/" + appID + "/" + contextID,

^

TypeError: Cannot read property 'getSteamID64' of null

My code

function sendRec(steamID, amount){
	if (!amount) {
        var amount = 1;
    }
	if (amount == 0) {
		console.log("User didn't provide a correct amount!");
		return;
	}
	
	manager.getUserInventoryContents(steamID, 440, 2, true, function (err, inventory){
		if (err) {
			console.log(err);
		} else {
			var scrap = inventory.filter(function (item) {
				return item.name == "Scrap Metal"
			});
			
			var refined = inventory.filter(function (item) {
				return item.name == "Refined Metal"
			});
				
			var NeededS = amount * 3
			var NeededR = amount / 3
			
			if (scrap.length === 0 && refined.length === 0){
				client.chatMessage(steamID, "It seems you don't have enough scrap.");
				return;
			} else if (amount > NeededS && amount > NeededR) {
				client.chatMessage(steamID, "You don't have enough scrap. You'll need " + left + " more scrap metals.");
				return;
			} else if (amount <= NeededS || amount <= NeededR) {
				manager.getInventoryContents(440, 2, true, function (err, inventory){
					if (err) {
						console.log(err);
					} else {
						var pool = inventory.filter(function (item) {
								return item.name == "Reclaimed Metal"
						});

						// Let the user know we don't have any
						if (pool.length === 0) {
							client.chatMessage(steamID, "I don't have available.  Sorry!");
							return;
						} else if (amount > pool.length) {
							console.log("User asked for more than my backpack.");
							client.chatMessage(steamID, "I only have " + pool.length + " available.  Sorry!");
							return;
						} else if (amount <= pool.length) {
							
							// Start a new trade offer
							var trade = manager.createOffer(steamID);
							
							// Add what we should to the current trade
							console.log("Adding " + amount + " rec.");
							
							
							if (scrap.length < NeededS) {
								if (Number.isInteger(NeededR) == false){
									return;
								} else {
									console.log("User doesn't have enough scrap. Sending REF OFFER!!");
									//USER ITEMS
									for (let i = 0; i < NeededR; i++) {
										trade.addTheirItem(refined[i]);
									}
									//BOT ITEMS
									for (let i = 0; i < amount; i++) {
										trade.addMyItem(pool[i]);
									}
								}							
							} else {
								console.log("User have enough scrap. Sending SCRAP OFFER!!");
								//USER ITEMS
								for (let i = 0; i < NeededS; i++) {
									trade.addTheirItem(scrap[i]);
								}
								//BOT ITEMS
								for (let i = 0; i < amount; i++) {
									trade.addMyItem(pool[i]);
								}
							}
							
							trade.setMessage("Here is your " + amount + " reclaimed metals");
							trade.send(function(err, status) {
								if (err) {
									console.log(err);
										return;
								} else if (status == 'pending') {
									console.log("Offer " + trade.id + "have been sent.");
									community.startConfirmationChecker(15 * 1000, config.identity);
									client.chatMessage(steamID, "Processing.");
									client.chatMessage(steamID, "Offer Sent!! Check your trade offer by here https://steamcommunity.com/tradeoffer/" + trade.id + "/.");
								} 
							});				
						}
					}
				});
			}
		}
	})
}

[TextDynasty]

Problem solved

[McMuffinDK]

Can you please post your solution so that someone else may learn from this?