Async parallel in NodeJS

Question

I'd like to know how to execute async functions, my goal is to uploads files and compress them... But it doesn't work because my files are not yet uploading when I write the .zip...

SO I get an empty .zip file...

var asyncTasks = [];

selectedPhotos.forEach(function(id){
  asyncTasks.push(function(callback){
    var newFileName = pathDir + '/' + id + '.jpg';
    api.media(id, function(err, media, remaining, limit) {
      gm()
      .in('-page', '+0+0')
      .in('./public/images/instabox.jpg')
      .in('-page', '+10+10')
      .in(media.images.thumbnail.url)
      .mosaic()
      .minify()
      .write(newFileName, function (err) {
        if (!err) console.log('done');
        if (err) console.log(err);
      });
    });
    callback();
  });
});

async.parallel(asyncTasks, function(){

  var admZip = new AdmZip();
  var pathDir = './public/uploads/'+reference;
  admZip.addLocalFolder(pathDir);
  var willSendthis = admZip.toBuffer();
  admZip.writeZip('./public/uploads/'+reference+'.zip');

});

Answer 1

You're calling the callback() too early. Move callback(); inside of your .write() callback like so:

.write(newFileName, function (err) {
  if (!err) console.log('done');
  if (err) console.log(err);
  callback(err);
});

When you execute the callback, that signifies that the task is finished. So without the above change, you're basically telling async that you're done immediately.