Helper method to get a value by searching for it by priority

First checking the options object passed in to the method call
then the instance object properties
or finally the global Steam object
function get(self, steamObj, key) {
    steamObj = steamObj || {};
    if (steamObj[key] !== undefined) {
        return steamObj[key];
    }
    else if (self[key] !== undefined) {
        return self[key];
    }
    else if (Steam[key] !== undefined) {
        return Steam[key];
    }
    else {
        throw new Error("Missing required field: "+key);
    }
}