How to return response from external function NodeJs

Question

I am new in NodeJs I am trying to get response from another function in Node Js. I am calling slug function in Nodejs. I have to get the slug before insert but always I geting response undefined I am used noejs package slugs

var slugs = require("slugs");

I am calling genslug(user.name) like this way .

genslug(connection,slugs(user.name),1,slugs(user.name),callback)

Created one function genslug like this

var genslug = function(connection,slug,counter=1,orgSlug,callback) {
    var query = connection.query('SELECT * FROM users WHERE slug = ?',slug,function(err,res) {
        if(err)
            callback({status: 'error', error : err});
        if(res.length > 0){
            counter++;
            slug = orgSlug+'-'+counter;
            genslug(connection,slug,counter,orgSlug,callback);
        }else{
            callback(false, slug);
        }
    });
}

But always I got undefined. Please response If anyone know this

Possible duplicate of [How do I return the response from an asynchronous call?](https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call) — Patrick Roberts, Jun 05 '18 at 04:46
Can you show your `slug` function from where you are calling? — abdulbarik, Jun 05 '18 at 04:55
slug : sluggen(connection,slugs(user.name),1,slugs(user.name),callback) — Raj, Jun 05 '18 at 05:08

score 0 · Answer 1 · answered Jun 05 '18 at 04:58

Understand the callback nature.

First argument always takes as error and second takes as success.

In your case it always execute in error block from were you are calling the function since you are passing else in final callback.

Try to remove false from final callback

var genslug = function(connection,slug,counter=1,orgSlug,callback) {
    var query = connection.query('SELECT * FROM users WHERE slug = ?',slug,function(err,res) {
        if(err)
            callback({status: 'error', error : err});
        if(res.length > 0){
            counter++;
            slug = orgSlug+'-'+counter;
            genslug(connection,slug,counter,orgSlug);
        }else{
            callback(null, slug);
        }
    });
}

how are you calling the `genslug` method? please update in question, your way of calling method is not proper. — abdulbarik, Jun 05 '18 at 05:10

score 0 · Answer 2 · answered Jun 05 '18 at 06:09

genslug(connection,slugs(user.name),1,slugs(user.name),function(err,resp){
   if(err)
   {
     console.log(err);
   }
   console.log(resp);
})

function genslug(connection,slug,counter=1,orgSlug,callback) {
    var query = connection.query('SELECT * FROM users WHERE slug = ?',slug,function(err,res) {
        if(err)
            callback(err,null);
        if(res.length > 0){
            counter++;
            slug = orgSlug+'-'+counter;
            //genslug(connection,slug,counter,orgSlug); - Callback function can't be call like this
        }else{
            callback(null, slug);
        }
    });
}

How to return response from external function NodeJs

2 Answers2