javascript - Conceptual: Create a counter in an external function -

i've written javascript download hundreds of files external site, using wget @ core.
after downloading of files, stuff them. issue is, files aren't of equal size. so, last wget formed isn't last file downloaded, meaning can't tell when last file has completed.

i do, however, know how many files there in total, , number associated each wget.

i have 3 js files, [parseproducts.js] ==> [createurl.js] ==> [downloadurl.js]

using information, how can tell when of files have been downloaded?

tried creating "ticker" function in file function resets on each instance, doesn't work @ all!

edit: code added didn't because didn't think people want trawl through it! i'm new programming/javascript/node. please let me know if there's better (i'm sure of more efficient!)

parseproducts.js

var fs = require('fs'); var iset = require('./ticker.js'); var createurl = require('./createurl.js'); var array = [];  filename = 'productlist.txt'; fs.readfile(filename, 'utf8', function(err, data) {   if (err) throw err;   content = data;   parsefile();  });  function parsefile() {     var stringarray = string(content).split(";");     (var index = 0; index < stringarray.length; ++index) {      createurl(stringarray[index],index,stringarray.length);     console.log(index+'/'+stringarray.length+' sent.');     if (index === 0) {          iset(true,stringarray.length);     } else {         iset (false,stringarray.length);     }      }; }; 

createurl.js

    function create(partnumber,iteration,total) {          var jsdownloadurl = require('./downloadurl.js');          jsdownloadurl(createurl(partnumber),partnumber,iteration,total);          function createurl(partnumber) {             var url = ('"https://data.icecat.biz/xml_s3/xml_server3.cgi?prod_id='+partnumber+';vendor=hp;lang=en;output=productxml"');             return url;         };     };  module.exports = create; 

downloadurl.js

function downloadurl(url,partnumber,iteration,total) {     // dependencies     var fs = require('fs');     var url = require('url');     var http = require('http');     var exec = require('child_process').exec;     var spawn = require('child_process').spawn;     var checkfiles = require('./checkfiles.js');      // app variables     var file_url = url;     var download_dir = './downloads/';      // downloading files directory, make sure it's there     var mkdir = 'mkdir -p ' + download_dir;     var child = exec(mkdir, function(err, stdout, stderr) {         if (err) throw err;         else download_file_wget(file_url);     });      // function download file using wget     var download_file_wget = function(file_url) {           // compose wget command         var wget = 'wget  --http-user="myaccount" --http-password="mypassword" -p ' + download_dir + ' ' + file_url;         // excute wget using child_process' exec function          var child = exec(wget, function(err, stdout, stderr) {         if (err) throw err;         else console.log(iteration+'/'+total+' downloaded.     '+partnumber + ' downloaded ' + download_dir);            });     }; };  module.exports = downloadurl; 

failed attempt ticker.js

function iset(bol,total) {     if (bol === true) {         var = 0;     } else {         var = 1;     };     counter(i, total); }    function counter(i,total) {     var n = n + i;     if (n === (total - 1)) {         var checkfiles = require('./checkfiles.js');         checkfiles(total);     } else {     console.log('nothing done');     }; }  module.exports = iset;       

update in response answer

this code looks now. however, error

child_process.js:945 throw errnoexception(process._errno, 'spawn'); ^ error: spawn emfile

// dependencies var fs = require('fs'); var url = require('url'); var http = require('http'); var exec = require('child_process').exec; var spawn = require('child_process').spawn; var checkfiles = require('./checkfiles.js');     function downloadurl(url,partnumber,iteration,total,clb) {     // app variables     var file_url = url;     var download_dir = './downloads/';      // downloading files directory, make sure it's there     var mkdir = 'mkdir -p ' + download_dir;     var child = exec(mkdir, function(err, stdout, stderr) {         if (err) throw err;         else download_file_wget(file_url);     });       var child = exec(mkdir, function(err, stdout, stderr) {         if (err) {             clb(err);         } else {             var wget = 'wget  --http-user="amadman114" --http-password="chip10" -p ' + download_dir + ' ' + file_url;              // excute wget using child_process' exec function             var child = exec(wget, function(err, stdout, stderr) {                 if (err) {                     clb(err);                 } else {                     console.log(iteration+'/'+total+' downloaded.     '+partnumber + ' downloaded ' + download_dir);                     clb(null);  // <-- can pass more args here if want, result                     // general convention callbacks take form of                     // callback(err, res1, res2, ...)                 }             });         }     }); };  function clb() {     var limit = 100,         errs = [];     (var = 0; < limit; i++) {         downloadurl(url,partnumber,iternation,total, function(err) {         if (err) {             errs.push(err);         }         limit--;         if (!limit) {             finalize(errs);         }         });     } }  function finalize(errs) {     // can check err     //or whatever stuff finalize code } module.exports = downloadurl; 

ok, have function downloadurl. need pass 1 more argument it: callback. , please, move requirements outside function , don't define function in function unless necessary:

var fs = require('fs'); // other dependencies , constants  function downloadurl(url,partnumber,iteration,total, clb) {  // <-- new arg     // code     var child = exec(mkdir, function(err, stdout, stderr) {         if (err) {             clb(err);         } else {             var wget = 'wget  --http-user="myaccount" --http-password="mypassword" -p ' + download_dir + ' ' + file_url;              // excute wget using child_process' exec function             var child = exec(wget, function(err, stdout, stderr) {                 if (err) {                     clb(err);                 } else {                     console.log(iteration+'/'+total+' downloaded.     '+partnumber + ' downloaded ' + download_dir);                     clb(null);  // <-- can pass more args here if want, result                     // general convention callbacks take form of                     // callback(err, res1, res2, ...)                 }             });         }     }); }; 

this nicer, doesn't it? when call function multiple times do:

var limit = 100,     errs = []; (var = 0; < limit; i++) {     downloadurl(..., function(err) {         if (err) {             errs.push(err);         }         limit--;         if (!limit) {             finalize(errs);         }     }); }  function finalize(errs) {     // can check err     //or whatever stuff finalize code } 

that's general idea. have tweak needs (in particular have modify intermediate function accept callback well). of course there libraries take care of kriskowal's q (q.all) or caolan's async (async.parallel).