Multer is a node.js middleware for handling multipart/form-data, which is primarily used for uploading files.
Below is an example of how to upload files using Node.js and Multer:
Firstly, you need to install Multer and then include it in your project:
```
npm install multer —save
```
```
var express = require(‘express’);
var multer = require(‘multer’);
var app = express();
```
Then, decide how multer should process incoming files. To store files on disk, use `multer.diskStorage` function, where you can determine the destination and filename for incoming files:
```
var storage = multer.diskStorage({
destination: function (req, file, cb) {
cb(null, ‘./uploads’) //specify the folder path where files get stored
},
filename: function (req, file, cb) {
cb(null, file.fieldname + ‘-’ + Date.now()) //specify the name of the file
}
})
var upload = multer({ storage: storage })
```
To handle post requests of incoming files use:
```
app.post(‘/upload’, upload.single(‘myFile’), function (req, res, next) {
// req.file is the ‘myFile’ file
// req.body will hold the text fields, if there were any
})
```
In this case, `upload.single(‘myFile’)` is the middleware for handling single file uploads where ‘myFile’ is the name of the file input field in the form.
Finally, start your server using:
```
app.listen(3000, function () {
console.log(‘Server started on port 3000’);
});
```
Now, if you send a POST request to the ‘/upload’ route with a file attached with the key ‘myFile’, it will be saved to the disk at the ‘./uploads’ path with its fieldname and current datestamp as the filename.
