Crafting a Minimalist File Upload API with Node.js and Express

Need a simple file upload API without the overhead of a full-blown framework? Today, we’ll craft a calm, minimalist solution using Node.js and Express.

Just pure backend bliss.

Why Keep It Simple?
Project Setup
Building the API
Testing the Upload
Next Steps

Why Keep It Simple?

A basic file upload service is a common sidekick:

Upload profile pictures
Submit documents
Store small attachments

By using only Node.js + Express with a sprinkle of Multer, we can avoid bloat and focus on clarity.

Project Setup

Let’s spin up a fresh project:

mkdir file-upload-api
cd file-upload-api
npm init -y
npm install express multer

Then create an entry file:

touch index.js

Building the API

Create the Express Server

// index.js
const express = require('express');
const multer = require('multer');
const path = require('path');

const app = express();
const PORT = 3000;

// Set storage engine
const storage = multer.diskStorage({
  destination: './uploads/',
  filename: (req, file, cb) => {
    cb(null, `${Date.now()}-${file.originalname}`);
  }
});

const upload = multer({ storage });

// Middleware
app.use(express.json());

// Upload endpoint
app.post('/upload', upload.single('file'), (req, res) => {
  if (!req.file) {
    return res.status(400).json({ message: 'No file uploaded.' });
  }
  res.status(201).json({ filename: req.file.filename });
});

// Start server
app.listen(PORT, () => console.log(`Server running on http://localhost:${PORT}`));

Create the Express Server

Make sure there’s a folder to store uploaded files:

mkdir uploads

Testing the Upload

You can test the API using Postman or cURL: Using cURL:

curl -F "file=@/path/to/your/file.jpg" http://localhost:3000/upload

You should receive:

{
  "filename": "timestamp-file.jpg"
}

And the file should appear inside the /uploads directory.

Using Postman:

Create a new POST request to http://localhost:3000/upload
Under “Body” select “form-data”
Add a field named file
Attach a file
Hit Send!

Next Steps

This calm little project can be expanded:
* Add file type restrictions (only images, only PDFs)
* Limit file size
* Integrate cloud storage (S3, Azure Blob)
* Add simple authentication

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Crafting a Minimalist File Upload API with Node.js and Express