In today’s digital age, the need to convert documents from one format to another is increasingly common. Whether it’s converting a Word document to a PDF or transforming an image into a text file, having a reliable document conversion service can be a valuable asset.

In this tutorial, we will explore how to build a document conversion service using Express.js, a popular web framework for Node.js, and document processing libraries like pdf-lib and tesseract.js.

Prerequisites

To follow along with this tutorial, you will need:

1. Node.js installed on your machine.
2. Basic knowledge of JavaScript and Express.js.

Setting up the Project

First, let’s create a new Express.js project by running the following commands in your terminal:

$ mkdir document-conversion-service
$ cd document-conversion-service
$ npm init -y

This will create a new project directory and initialize a new package.json file with default settings.

Next, we need to install Express.js and the required document processing libraries. Run the following command in your terminal:

$ npm install express pdf-lib tesseract.js

Once the installation is complete, we can start building our document conversion service.

Creating the Express.js Server

Create a file called index.js in the project directory and add the following code:

const express = require('express');
const { createWorker } = require('tesseract.js');

const app = express();
const worker = createWorker();

app.use(express.json());

// Endpoint for document conversion
app.post('/convert', async (req, res) => {
  const { fileUrl } = req.body;

  await worker.load();
  await worker.loadLanguage('eng');
  await worker.initialize('eng');

  const { data: { text } } = await worker.recognize(fileUrl);
  const pdfDoc = await PDFLib.PDFDocument.create();
  const page = pdfDoc.addPage();
  page.drawText(text);

  const pdfBytes = await pdfDoc.save();

  res.setHeader('Content-Type', 'application/pdf');
  res.send(pdfBytes);
});

const PORT = 3000;
app.listen(PORT, () => {
  console.log(`Server is running on port: ${PORT}`);
});

In the code above, we import necessary packages and create an Express.js application. We define a route /convert to handle the document conversion. When a POST request is made to this endpoint, we download the document from the provided fileUrl, perform OCR using Tesseract.js, and create a PDF document using pdf-lib. Finally, we send the converted PDF as a response to the client.

Starting the Server

To start the server, run the following command in your terminal:

$ node index.js

Your document conversion service is now running on http://localhost:3000.

Conclusion

In this tutorial, we learned how to build a document conversion service using Express.js and document processing libraries. We explored the process of converting documents to PDF format by performing optical character recognition (OCR) on the content.

With this knowledge, you can enhance the functionality of your application by implementing additional document conversion capabilities and integrating with various document processing libraries available to you.

#documentconversion #expressjs