R3v3rso

The first problem I see is that you aren't handling the callback to offer.accept, which could fail.
 
Secondly, you can use the fs module to read from a file. If it's newline-delimited, you could call split("\n") to get an array containing each line in the file.

Do something like this:
let isEachItemATradingCard = theirItems.every((item) => { if (item.appid != 753 || item.contextid != 6) { // AppID is not "Steam" or contextid is not "Community" return false; } let tag = item.getTag('item_class'); if (!tag || tag.internal_name != 'item_class_2') { // Not a trading card                 // You could also check that tag.localized_tag_name == 'Trading Card' but that would only work for English return false; } return true; // all checks passed });