Multer Filefilter Invalid File Uploaded Results In Client Page Getting Stuck Loading Incomplete Html File Cập Nhật Mới

When using Multer to upload files in a Node.js application, it’s important to properly handle errors that may occur during the file upload process, such as invalid file types being uploaded.

One way to handle this is to provide a fileFilter function to Multer, which can be used to check whether an uploaded file meets certain criteria, such as its file type. If the file does not meet the criteria, the fileFilter function can return an error to indicate that the file is invalid.

To prevent the client page from getting stuck loading an incomplete HTML file when an invalid file is uploaded, you can ensure that your Node.js application properly handles errors that may occur during the file upload process. Specifically, you can use error handling middleware to catch any errors that occur during file upload and return an appropriate response to the client.

Here’s an example of how you can use error handling middleware in your Node.js application to handle errors that may occur during file upload:

javascript
const express = require('express');
const multer = require('multer');

const app = express();

const storage = multer.diskStorage({
  destination: function (req, file, cb) {
    cb(null, 'uploads/')
  },
  filename: function (req, file, cb) {
    cb(null, file.fieldname + '-' + Date.now())
  }
});

const upload = multer({
  storage: storage,
  fileFilter: function(req, file, cb) {
    // check file type and return error if invalid
    if (!file.originalname.match(/\.(jpg|jpeg|png)$/)) {
      return cb(new Error('Invalid file type'));
    }
    cb(null, true);
  }
});

app.post('/upload', upload.single('file'), function(req, res) {
  res.send('File uploaded successfully');
});

// error handling middleware
app.use(function(err, req, res, next) {
  if (err instanceof multer.MulterError) {
    res.status(400).send('Error uploading file');
  } else if (err) {
    res.status(400).send(err.message);
  } else {
    next();
  }
});

app.listen(3000, function() {
  console.log('Server listening on port 3000');
});

In this example, we’re using the multer.MulterError class to detect errors that occur during file upload. If a Multer error occurs, we return a 400 status code and an appropriate error message to the client. If any other error occurs, we also return a 400 status code and the error message.

By properly handling errors during file upload, you can ensure that your client page does not get stuck loading an incomplete HTML file. Instead, the client will receive an appropriate error message indicating that the file upload failed.