Nodejs save uploaded file - node.js

Question

I have an application and in that application, I want to use some file upload mechanism.
My requirement is:
Once the file is uploaded, its name will be changed to something unique, like uuid4(). I will store this name in the database later.
I have written something like that, however I have a couple of questions:
const multer = require('multer');
const upload = multer();
router.post('/', middleware.checkToken, upload.single('file'), (req,res,next)=>{
// key:
// file : "Insert File Here"
console.log("req:");
console.log(req.file);
const str = req.file.originalname
var filename = str.substring(0,str.lastIndexOf('.'));
// I will use filename and uuid for storing it in the database
// I will generate unique uuid for the document and store the document
// with that name
var extension = str.substring(str.lastIndexOf('.') + 1, str.length);
// HERE!
res.status(200).json();
})
I have seen examples of storing it in the diskStorage:
var storage = multer.diskStorage({
destination: function (req, file, cb) {
cb(null, '/tmp/my-uploads')
},
filename: function (req, file, cb) {
cb(null, file.fieldname + '-' + Date.now())
}
})
var upload = multer({ storage: storage })
However, as far as I understood, this is a configuration outside of the API call. Meaning that I cannot modify it every time I call this API. I want to assign different names to the file, and I need that name(uuid) to save that name in the database.
How can I preserve such functionality?

Answer 1

Thanks to #Rashomon and #Eimran Hossain Eimon, I have solved the issue. In case of anyone wonders the solution, here it is:
const multer = require('multer');
var storage = multer.diskStorage({
destination: function (req, file, cb) {
// the file is saved to here
cb(null, '/PATH/TO/FILE')
},
filename: function (req, file, cb) {
// the filename field is added or altered here once the file is uploaded
cb(null, uuidv4() + '.xlsx')
}
})
var upload = multer({ storage: storage })
router.post('/', middleware.checkToken, upload.single('file'), (req,res,next)=>{
// the file is taken from multi-form and the key of the form must be "file"
// visible name of the file, which is the original, uploaded name of the file
const name = req.file.originalname;
// name of the file to be stored, which contains unique uuidv4
const fileName = req.file.filename;
// get rid of the extension of the file ".xlsx"
const file_id = fileName.substring(0, fileName.lastIndexOf('.'));
// TODO
// Right now, only xlsx is supported
const type = "xlsx";
const myObject = new DatabaseObject({
_id : new mongoose.Types.ObjectId(),
file_id: file_id,
name : name,
type: "xlsx"
})
myObject .save()
.then(savedObject=>{
// return some meaningful response
}).catch(err=>{
// return error response
})
})
This solves my current issue. Thanks for helping. For future improvements, I'll add error case for:
In case uuidv4 returns an id which already exists(I believe it is highly unlikely since the object contains some timestamp data), rerun the renaming function.
In case there is an error in saving to the database, I should delete the uploaded file to avoid future conflicts.
If you have solutions for those problems too, I'm much appreciated.

Answer 2

I think you got it wrong... you said that
I cannot modify it every time I call this API.
But actually, the filename is called every time for every file. Let me explain this portion of code...
filename: function (req, file, cb) {
cb(null, file.fieldname + '-' + Date.now())
}
Here look at the callback function (denoted by cb) :
1st argument null in callback function is like convention. You always pass null as the first argument in a callback function. See this Reference
2nd argument determines what the file should be named inside the destination folder. So, here you can specify any function, which can return you a unique filename every time.
Since you are using mongoose...
I think it would be better if you implement your function uniqueFileName() using the mongoose method within your Schema (in which you want to save the file path) and call it in your route handler. Learn More

Answer 3

No need. Because you're using timestamps.
In case of an error in saving to the database, you can delete the uploaded file using this code to avoid future conflicts. Try this:
const multer = require('multer');
const fs = require('fs'); // add this line
var storage = multer.diskStorage({
destination: function (req, file, cb) {
// the file is saved to here
cb(null, '/PATH/TO/FILE')
},
filename: function (req, file, cb) {
// the filename field is added or altered here once the file is uploaded
cb(null, uuidv4() + '.xlsx')
}
})
var upload = multer({ storage: storage })
router.post('/', middleware.checkToken, upload.single('file'), (req,res,next)=>{
// the file is taken from multi-form and the key of the form must be "file"
// visible name of the file, which is the original, uploaded name of the file
const name = req.file.originalname;
// name of the file to be stored, which contains unique uuidv4
const fileName = req.file.filename;
// get rid of the extension of the file ".xlsx"
const file_id = fileName.substring(0, fileName.lastIndexOf('.'));
// TODO
// Right now, only xlsx is supported
const type = "xlsx";
const myObject = new DatabaseObject({
_id : new mongoose.Types.ObjectId(),
file_id: file_id,
name : name,
type: "xlsx"
})
myObject .save()
.then(savedObject=>{
// return some meaningful response
}).catch(err=>{
// add this
// Assuming that 'path/file.txt' is a regular file.
fs.unlink('path/file.txt', (err) => {
if (err) throw err;
console.log('path/file.txt was deleted');
});
})
})
also see NodeJS File System Doc