NodeJs function wait until callback return value

Question

I want to print the value of var a outside the function call. If I run this program, it prints undefined.

var http = require('http');

var foo = function(req, res){
    var a = xyz('5',function(aa){
        console.log(aa);
        return aa;
    });
    res.end(a);
    console.log(a);
}

function xyz(arg,callback){
    var aa = 55;
    return callback(aa);
}

http.createServer(foo).listen(8000);
console.log('start server');

What is the link between your title and the question ? Where exactly do you try to print `a` ? — Derlin, Mar 04 '19 at 12:58
You should visit here first before asking question : https://stackoverflow.com/help/how-to-ask — G2 Jakhmola, Mar 04 '19 at 13:02

score 0 · Accepted Answer · answered Mar 04 '19 at 13:17

0

make your function async and then await xyz()

var http = require('http');

var foo = async function(req, res){
  var a = await xyz('5'); 
  res.end(a);
  console.log(a);
}

function xyz(arg){
  var aa = 55;
  return aa;
}

http.createServer(foo).listen(8000);
console.log('start server');

answered Mar 04 '19 at 13:17

Basit

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don't forget to accept the answer if your problem solved – Basit Mar 04 '19 at 13:24
How set response to browser ? – Shekhar Mittal Mar 04 '19 at 13:41

NodeJs function wait until callback return value

1 Answers1