what is the argument "arguments" passed to exec function in mongoose? - node.js

Question

i've been trying to use cache with redis in my nodejs mongodb application but i didn't find any tutorial on how to do that except few which are using logic that seems to not be explained in mongoose documentation
const exec = mongoose.Query.prototype.exec;
mongoose.Query.prototype.exec = async
function (){
// our caching logic
return await exec.apply(this, arguments);
}
where does arguments come from ? because it seems to be undefined yet it is used
mongoose.Query.prototype.exec = async function(){
const collectionName = this.mongooseCollection.name;
if(this.cacheMe){
// You can't insert json straight to redis needs to be a string
const key = JSON.stringify({...this.getOptions(),
collectionName : collectionName, op : this.op});
const cachedResults = await redis.HGET(collectionName,key);
// this.op is the method which in our case is "find"
if (cachedResults){
// if you found cached results return it;
const result = JSON.parse(cachedResults);
return result;
}
//else
// get results from Database then cache it
const result = await exec.apply(this,arguments);
redis.HSET(collectionName, key, JSON.stringify(result) , "EX",this.cacheTime);
//Blogs - > {op: "find" , ... the original query} -> result we got from database
return result;
}
clearCachedData(collectionName, this.op);
return exec.apply(this,arguments);
}
and what is this.getOptions()?
i would be thankful if any one can explain me this logic, because i did not find any help in the documentations nor internet blogs and articls

Answer 1

The arguments object is a local variable that is available inside every function in JavaScript and contains the values of the arguments passed to the function.
this.getOptions() is the local method that returns the options to the query.
// A key example for mongoose Redis integration
const key = JSON.stringify({
collectionName: this.mongooseCollection.name,
op: this.op,
options: this.getOptions(),
filter: this.getFilter(),
projection: this.projection(),
populatedPaths: this.getPopulatedPaths(),
});
There are a lot of similar packages on NPM, but I highly recommend standard mongoose and redis ones to get up and running. I assumed your initialization point was similar to this post. This can also be a relevant source.