returning undefined before data -- callback implemented --please help

[wasiu razak]

am trying to grab data from a function , by passing in a args and return data 

but when i run i get undefined before i get the data , i have wrapped it in a time still same output 

version 2

function citifmonlineDetail(url, callback) {

setTimeout(function() {

request(url, function(error, response, html) {

var detail = "";

if (!error) {

$ = cheerio.load(html);

$('.entry p').each(function(index, paragraphs) {

console.log($(paragraphs).text());

var a = $(paragraphs).text();

detail = detail.concat(a + " ");

});

callback(detail);

}

});

}, 3000);

}

var citi = 'http://citifmonline.com/2015/12/01/no-bias-in-disbursing-leap-funds-gender-minstry-insists/';

var data= citifmonlineDetail(citi,function(result) {

return result;

}) ;

console.log(data);

version 1

function citifmonlineDetail(url) {
request(url, function(error, response, html) {
    if (!error) {
        $ = cheerio.load(html);
        var b;

        $('.entry p').each(function(index, paragraphs) {
            var a =$(paragraphs).text();
            b =b.concat(a);

        });
        return b 
    }
});

}

[Mohan Kumar]

  HI Wasiu ,

  The problem you are facing is the async behaviour of JavaScript.

  when the function 
citifmonlineDetail(citi,function(result) {

return result;

}) ; 

is called  the function directly returns undefined , since the function not containing  return statement.

There are two ways to solve 

1) simply changing to 
var data ;

citifmonlineDetail(citi,function(result) {

data =  result;
        console.log(data);

}) ;

2)  BY using promise 

 var promise = new Promise(function(resolve) {

  // do a thing, possibly async, then…

    function hello(){

       setTimeout(function(){

          debugger;

          resolve("hello");

       },1000)

    };

    hello();

});

promise.then(function(val){

     data = val;

     console.log(data);

  });

   

[wasiu razak]

thanks so much , guess i still need to revisit callbacks and promises ,though i understood it , thanks again 

[Zlatko]

On Thursday, December 3, 2015 at 3:30:07 PM UTC+1, wasiu razak wrote:

thanks so much , guess i still need to revisit callbacks and promises ,though i understood it , thanks again 

We all think we understand them, and we all often fail :) That's why it's called callback hell.