File data(Image, pdf) is not getting pushed into the MongoDB array - node.js

Question

Whenever I upload the new file from the postman it overwrites existing file and save one and only uploaded file.
I have tried document.push method but it logs the error that "TypeError: documents.push is not a function" But when I log console.log(documents) it logs in an array. Am I doing something wrong?
The multer function to handle file uploading:
var storage = multer.diskStorage({
destination: function (req, file, cb) {
cb(null, "./src/uploads/");
},
filename: function (req, file, cb) {
cb(
null,
file.fieldname + "-" + Date.now() + path.extname(file.originalname)
);
},
});
var upload = multer({
storage: storage,
fileFilter: function (req, file, cb) {
var filetypes = /jpeg|jpg|png|pdf/;
var mimetype = filetypes.test(file.mimetype);
var extname = filetypes.test(path.extname(file.originalname).toLowerCase());
if (mimetype && extname) {
return cb(null, true);
}
cb("Please upload valid file");
},
}).array("documents");
The uploadDocument service file:
exports.uploadDocuments = async (id, documents, file) => {
let files = documents.push(file);
let document = await User.findByIdAndUpdate(
{ _id: id },
{ $set: { documents: files, registration_process_value: 99 } },
{ new: true }
);
return document;
};
The userController to upload the file:
exports.updateDocuments = catchAsync(async (req, res) => {
try {
check_user = await userService.getUser(req.data.id);
if (!check_user) return res.status(404).json({ message: "User not found" });
if (check_user.registration_process_value >= 4) {
let uploadDocument = await userService.uploadDocuments(
check_user.id,
check_user.documents,
req.files
);
return res.status(200).json({ data: uploadDocument });
}
} catch (error) {
return res.status(400).json({ message: error });
}
});
The documents type is Array in the schema like following:
documents: {
type: Array,
}
documents.push(file) is returning a number (like if I console.log(files) after sending the request from the postman then it returns "files -> 2"). It is not pushing the actual data of the file.

Answer 1

First you push a file into documents and store the new length of the array in files:
let files = documents.push(file);
Then you set the documents field to that array length:
let document = await User.findByIdAndUpdate(
{ _id: id },
{ $set: { documents: files, registration_process_value: 99 } },
{ new: true }
);
I assume that you want to store the actual array:
{ $set: { documents: documents, registration_process_value: 99 } }
Instead of using $set to replace the entire documents array, I would suggest using $push:
{
$set: { registration_process_value: 99 },
$push: { documents : file }
}
EDIT: if file is actually an array of file objects, instead of a single object, things change a bit.
If you still want to use push:
documents.push(...file);
With $push, you need to use $each:
{
$push : { documents : { $each : file } }
}