callback function issues Node.js

Question

function addToServer(myid) {
    console.log("jayesh"+db.server.find({id:myid})+"\n");
    return db.server.find({id:myid});
};
addToServer(myid,function(resp) {
    console.log("something");
    if(resp.count()>0)
        console.log("present");
    else
        console.log("Nope");
});

I want to know whether document with id = myid is present in server collection. I guess there is some issue with callback but being a novice don't have much a knowledge about it. Please help me out.Thanks

P.S For function I am getting output saying "jayesh[object Object] " and nothing is printing for callback method.

Well, that db.find call is async, so you have to wait for an answer (callback) -- and go from there. — tymeJV
– tymeJV, Commented Jan 13, 2014 at 19:51

Community · Accepted Answer · 2017-05-23 12:03:47Z

2

The problem is you trying to write synchronous code inside an asynchronous environment.

You need to pass callbacks:

function addToServer(myid, cb) {
    db.server.find({id:myid},cb);
};

addToServer(myid,function(err, resp) {
    if(err) {
      console.log("err");
    } else if(resp.count()>0) {
      console.log("present");
    } else {
      console.log("Nope");
    }
});

In async programming you cannot throw and cannot return you use callbacks instead!

These callbacks are conventionally invoked with an error object (alternative to throw) as the first argument and all other arguments with the returned data (alternative to return).

Reading Material on Async Programming Practices

edited May 23, 2017 at 12:03

CommunityBot

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answered Jan 13, 2014 at 20:04

Ilan Frumer

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