Download a file from web using Node js and loop

Question

I want to download multiple files from the web using this code:

    var fs = require('fs');
    var http = require('http');
    var request = require('request');

    var file;
    for(var i = 1; i <= 5; i++) {
         //CHECK IF REMOTE FILE EXISTS
         request('http://webaddress.com/filename' + i + '.jar', function (err, resp) {

         //IF EXISTS DO
         if (resp.statusCode == 200) {
             //DOWNLOAD DATA AND CREATE A NEW .JAR FILE
             file = fs.createWriteStream('D:\\filename' + i + '.jar');
             http.get('http://webaddress.com/filename' + i + '.jar', function(response) {
                  response.pipe(file);
                  file.on('finish', function() {
                      file.close();
                  });
             });
         }

         //FILE DOES NOT EXIST
         });
     }

The result I want is: multiple files downloaded with filenames filename1-5.jar. The result I am getting is just 1 file with filename filename5.jar (or the last value of the i var in the loop). What am I doing wrong?

Your request is asynchronous and it will execute only after your loop finishes hence the 5 from the filename. — Ionut Necula
– Ionut Necula, Commented Jul 16, 2018 at 11:47
See this answer, it can help you solve your problem stackoverflow.com/a/19911657/8221063 — Lucas Duarte
– Lucas Duarte, Commented Jul 16, 2018 at 11:52

BraveButter · Accepted Answer · 2018-07-16 15:00:57Z

3

Like @Ionut said your requests are async so you need to wait for it

let fs = require('fs');
let request = require('request');

let download = (uri, filename) => {
    return new Promise ((resolve, reject) => {
        request.head(uri, function(err, res) {

            if (res.statusCode === 200) {
                request(uri).pipe(fs.createWriteStream(filename)).on('close', resolve);
            } else {
                reject(res.statusCode);
            }
        });
    });
};

let promises = [];

for(let i = 1; i <= 5; i++) {
    promises.push(download('http://webaddress.com/filename' + i + '.jar', 'D:\\filename' + i + '.jar'));
}

Promise.all(promises).then(() => {
    process.exit(0);
});

answered Jul 16, 2018 at 15:00

BraveButter

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Comments

Ionut Necula · Accepted Answer · 2018-07-16 12:05:12Z

2

Your request is asynchronous and it will execute only after your loop finishes hence the 5 from the filename. A solution for this is to threat your code separately by creating a new function and call it inside the loop:

var fs = require('fs');
var http = require('http');
var request = require('request');

var file;

function customRequest(i){

  //CHECK IF REMOTE FILE EXISTS
  return request('http://webaddress.com/filename' + i + '.jar', function(err, resp) {

    //IF EXISTS DO
    if (resp.statusCode == 200) {
      //DOWNLOAD DATA AND CREATE A NEW .JAR FILE
      file = fs.createWriteStream('D:\\filename' + i + '.jar');
      http.get('http://webaddress.com/filename' + i + '.jar', function(response) {
        response.pipe(file);
        file.on('finish', function() {
          file.close();
        });
      });
    }

    //FILE DOES NOT EXIST
  });

}

for (var i = 1; i <= 5; i++) {
   customRequest(i)
}

edited Jul 16, 2018 at 12:05

answered Jul 16, 2018 at 11:56

Ionut Necula

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1 Comment

lupu51nfactum N778 Over a year ago

Thanks, your code does make 5 separate files. The issue I have now is that all data goes to just 1 random file, others are empty. Could this be that the function is executed too fast? I tried setTimeout without much luck.

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