index.js
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);
    }
}
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);
    }
}
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