global variable in nodejs

Question

I try every possible solution that is available in SO. like using global or using bind but can not access the global variable. here is my code i am trying to generate sitemap in nodejs here is my .js file.

    module.exports = function (portal) {
    var mongoose = require('mongoose');
    var News = mongoose.model('News');
    var urls ="";
    var gensitemap =  function(){
    urls = "abc";

    console.log(urls);// print abc as expected
    News.find().exec(function (err, news) {
      news.forEach(function (t) {
        urls += "<url><loc>"+cdn_url+"/news"+t.slug+"</loc>"+"</url>";
       });
    });
    console.log(urls);// print still abc as not  expected it should be change
    }   
    var allUsers = portal.setupContext({});
    app.get('/gensitemap',allUsers ,gensitemap);
  };

here you can see i use url variable befor and after News.find() method.but instead of change the url its is printing same output.

Any idea i already try global or async.parallel({}) but same issue in News.find() node js treat that variable as different.

Any help ?

UPDATE :

After reading the comments and some of the mention question i try this

    Events.find().exec(function (err1, events) {
            events.forEach(function (t1) {
                url += "<url><loc>"+cdn_url+"/event"+t1.slug+"</loc>"+changefreq+priority+"</url>";
            });
            News.find().exec(function (err2, news) {
                    news.forEach(function (t2) {
                        url += "<url><loc>"+cdn_url+"/news"+t2.slug+"</loc>"+changefreq+priority+"</url>";
                    });
                    var static_urls = ['about-us','categories','overview','media','contact-us','login','register','pages/en/faq'];
                            for(var i = 0 ;i < static_urls.length;i++){
                                url += "<url><loc>"+"http://192.168.10.38:3000/"+static_urls[i]+"</loc>"+"<changefreq>weekly</changefreq>"+"<priority>1</priority>"+"</url>";
                            }
                    console.log(url);

//this url(variable) print only the changes i made in above for loop.. :-(
                });
        });

I also notice after waiting some time i am able to see the change but they are not in same order.

Possible duplicate of How to return the response from an asynchronous call? — baao
– baao, Commented Nov 20, 2017 at 11:24
try to this link and slove qution; stackoverflow.com/questions/10987444/… — Dharmik Unagar
– Dharmik Unagar, Commented Nov 20, 2017 at 11:24
Yes it is. The answers to the question solve exactly your problem. But keep trying to do something with global variables if you know it better... :-) — baao
– baao, Commented Nov 20, 2017 at 11:28
Your problem is you don't understand the life cycle of an asynchronous call in NodeJS. You don't need to use global or async (using global is an 95% bad idea in all cases). Your just need to understanding is useless to try too access urls before mongo reply to your request. — Techniv
– Techniv, Commented Nov 20, 2017 at 13:09

Kishan Oza · Accepted Answer · 2017-11-21 07:11:28Z

1

    module.exports = function (portal) {
    var mongoose = require('mongoose');
    var News = mongoose.model('News');
    var urls ="";
    var gensitemap =  function(){
    urls = "abc";

    console.log(urls);// print abc as expected
    News.find().exec(function (err, news) {//this block of code gets executed after the News.find().exec() function return . Anything you want to do after the exec function call get a response you have to do it here. inside this call back function.

      news.forEach(function (t) {
        urls += "<url><loc>"+cdn_url+"/news"+t.slug+"</loc>"+"</url>";
       });
      //if you log the url here you should find ur desired value
      console.log(urls);
    });
    //This is getting called before your News.find().exec() function returns any value.
    console.log(urls);// print still abc as not  expected it should be change
    }   
    var allUsers = portal.setupContext({});
    app.get('/gensitemap',allUsers ,gensitemap);
  };

edited Nov 21, 2017 at 7:11

Kishan Oza

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answered Nov 20, 2017 at 13:12

Mustafa Mamun

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3 Comments

Foram Sangani Over a year ago

Look i agree in the News.find() call back i get my desire out put but i have more 3 other call like News.find() then what i suppose to do ?

Mustafa Mamun Over a year ago

depends on how you want to use them. You can look at these packages. npmjs.com/package/async or bluebirdjs.com/docs/getting-started.html

Techniv Over a year ago

Or the classic ES6 Promise

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