Disable automatic upload with Multer

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I'm using multer for the first time and I noticed the image is always uploaded.

Now my problem is that I would like to do some data validation on the body of the request with Joi, then move the file in the appropriate folder if the data validation is a success.

Is it possible with Multer and how would you achieve this ?

Or, is there a way to disable the automatic upload with Multer and move the file manually once the data validation is done ?

Thanks a lot for your help.

multer multipartform-data javascript
1 Answers

There are multiple ways to do this. You could use a custom middleware doing validation before Multer, or you could manage the validation within Multer directly. Here is an example using the default DiskStorage:

const storage = multer.diskStorage({
  destination: function (req, file, cb) {
    const valid = ...; // your validation logic
    if (valid) cb(null, '/tmp/my-uploads');
    else cb(new Error('Validation failed.'));
  },
});

const upload = multer({ storage: storage });

If you need more control, you can use MemoryStorage:

const storage = multer.memoryStorage();
const upload = multer({ storage: storage });

app.post('/xyz', upload.single('file'), (req, res) => {
  // because of memoryStorage, the file will be available in a buffer
  // do your validation logic here, and when you are happy write the buffer to the disk
});

Read more about storage in the docs.

user_63533650
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