Upload files in node using multer

Multer is used to upload files in Node JS and express js. Multer supports Multi Part forms only. To use multer to upload files, use enctype multipart/form-data in html form.

By default, all form in html are application/x-www-form-urlencoded. But Multer will works only with multipart/form-data.

Install Multer

npm i multer


Multipart Form

Multer use Multipart form only. By default in HTML, all forms are using enctype application/x-www-form-urlencoded. So tio use multer, set enctype multipart/form-data in html form.

Multipart encoding send uploaded file data in parts. That's why its call Multipart.


<form action="/upload" method="post" enctype="multipart/form-data">
    
<label>Upload Picture: <input type="file" name="pic"> </label>

</form>

Multer usage

Multer can be used to upload single or multiple files. Here are some live examples of how to upload single or multiple files using multer.

Multer Example

     
const express=require('express');
const app=express();
const multer  = require('multer')
const upload = multer({ dest: 'src/public/uploads/' })

    
app.post('/upload',upload.single('pic'),(req,res)=>{
    // req.file is the picture
    // req.body is text inputs
    res.status(200).send("File Uploaded");
});

app.listen(3000,()=>{
console.log(`App running`);
});

Upload Multiple files

 
const express=require('express');
const app=express();
const multer  = require('multer')
const upload = multer({ dest: 'src/public/uploads/' })

app.post('/upload',upload.array('pics',4),(req,res)=>{
    // req.files is array of files
    // req.body is text inputs
    res.status(200).send("Files Uploaded");
});

app.listen(3000,()=>{
console.log(`App running`);
});

Upload Files with fields


const express=require('express');
const app=express();
const multer  = require('multer')
const upload = multer({ dest: 'src/public/uploads/' })
    
const fields=upload.fields([
    { name: 'pic', maxCount: 1 },
    { name: 'gallery', maxCount: 4 }
]);

app.post('/upload',fields,(req,res)=>{
    // req.files['pic'][0] is file
    // req.files['gallery'] is array of files
    res.status(200).send("Files Uploaded with fields");
});
    
app.listen(3000,()=>{
console.log(`App running`);
});    


storage

disk storage engine gives full control to store files. disk storage gives two options, destination and filename. We can also change file name using disk storage engine. See example


  const express=require('express');
  const app=express();

  const multer  = require('multer');
  
  const storage = multer.diskStorage({
    destination: function (req, file, cb) {
      cb(null, 'src/public/uploads/')
    },
    filename: function (req, file, cb) {
      cb(null, Date.now() + path.extname(file.originalname)) 
    }
  });
const upload=multer({storage:storage});

  
  app.post('/upload',fields,(req,res)=>{
      res.status(200).send("Files Uploaded with fields");
  });
      
  app.listen(3000,()=>{
  console.log(`App running`);
  });