Adding mongoose object to array in nodejs

Question

I have an array of images as this.

  var newImageParams = [
    {
      image_string: "hello",
      _type: "NORMAL"
    },
    {
      image_string: "hello",
      _type: "NORMAL"
    }
  ]

I am using mongo db and In nodejs, I am using mongoose, Everything is fine, I Can add data to mongoose table, but after adding each image, I am trying to save the resulting object into an array, Which in console.log is happening and right as well, but when I return that array, there is nothing in it and it empty

if (newImageParams) {
  for (var i = newImageParams.length - 1; i >= 0; i--) {
    // allImages[i]
    var newImage = new Image(Object.assign(newImageParams[i], {bike: bike._id}));
    newImage.save(function(err, image){
      console.log(image);
      allImages.push(image);
      console.log(allImages);
    });
  }
}

This is what I am doing, everything is right and good in console but when I finally return,

res.json({bike: bike, images: allImages });

Images array is totally empty as it was when declared? why this is happening, please help

post the full code block

Tushar Gupta - curioustushar
– Tushar Gupta - curioustushar

2017-07-17 14:45:14 +00:00
Commented Jul 17, 2017 at 14:45 — Tushar Gupta - curioustushar
– Tushar Gupta - curioustushar, Commented Jul 17, 2017 at 14:45

Lazyexpert · Accepted Answer · 2017-07-17 15:45:20Z

2

I bet you send response before your callbacks are done.

The easy and fast fix:

if (newImageParams) {
  for (var i = newImageParams.length - 1; i >= 0; i--) {
    const image = Object.assign(newImageParams[i], {bike: bike._id});
    var newImage = new Image(image);
    allImages.push(image);
    newImage.save(function(err, image){
      console.log(image);
      console.log(allImages);
    });
  }
}

I will add correct approach with async/await, the older versions would use Promise.all or async.parallel:

async function doJob() {
  if (newImageParams) {
    for (var i = newImageParams.length - 1; i >= 0; i--) {
      const image = Object.assign(newImageParams[i], {bike: bike._id});
      const newImage = new Image(image);      
      await newImage.save();
      allImages.push(image);
    }
  }
}

edited Jul 17, 2017 at 15:45

answered Jul 17, 2017 at 14:49

Lazyexpert

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6 Comments

Junaid Farooq Over a year ago

why cant we add the actual image object to array?

Lazyexpert Over a year ago

@JunaidFarooq I've updated my answer, hope this will help you understand the issue.

Junaid Farooq Over a year ago

where to add and call this method?

Lazyexpert Over a year ago

Can you specify, what node version you have? Or maybe you can update it to latest?

Junaid Farooq Over a year ago

v6.11.1 here you go

|

HuyTran · Accepted Answer · 2017-07-17 16:00:27Z

0

allImages.push(image); -> that line of code is async. It's will go to event queue and your console log will call immediately.

So console.log(allImages); will return empty.

You can read more in here. It will help you in future.

answered Jul 17, 2017 at 16:00

HuyTran

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