Build an Invoice Processor with Node.js and the AllPDFMagic API

Invoice processing is one of the highest-ROI automation opportunities in any business. Manually keying invoice data from PDFs into accounting software takes 2-5 minutes per invoice — and introduces errors. A Node.js script using the AllPDFMagic API can process the same invoice in under 2 seconds and output clean JSON or CSV.

This guide builds a production-ready invoice processor: accepts PDF invoices from a folder, extracts structured data, and writes a CSV ready for accounting import.

Setup

mkdir invoice-processor && cd invoice-processor
npm init -y
npm install node-fetch form-data dotenv

Create a .env file:

ALLPDFMAGIC_API_KEY=apm_live_your_key_here

Core extractor module

// extractor.js
import fetch from 'node-fetch';
import FormData from 'form-data';
import { createReadStream } from 'fs';
import { basename } from 'path';
import 'dotenv/config';

const API_KEY = process.env.ALLPDFMAGIC_API_KEY;
const BASE_URL = 'https://www.allpdfmagic.com/api/v1';

export async function extractInvoice(filePath) {
  const form = new FormData();
  form.append('file', createReadStream(filePath), {
    filename: basename(filePath),
    contentType: 'application/pdf',
  });

  const res = await fetch(`${BASE_URL}/ai/extract-invoice`, {
    method: 'POST',
    headers: {
      Authorization: `Bearer ${API_KEY}`,
      ...form.getHeaders(),
    },
    body: form,
  });

  if (res.status === 429) throw new Error('QUOTA_EXCEEDED');
  if (!res.ok) {
    const err = await res.json().catch(() => ({}));
    throw new Error(err.error || `HTTP ${res.status}`);
  }

  const data = await res.json();
  return { ...data, _source: basename(filePath) };
}

CLI processor with retry

// process.js
import { glob } from 'glob';
import { extractInvoice } from './extractor.js';
import { writeFileSync, mkdirSync } from 'fs';
import { join } from 'path';

const INPUT_DIR = process.argv[2] || './invoices';
const OUTPUT_DIR = process.argv[3] || './output';
const CONCURRENCY = 3;
const RETRY_DELAY_MS = 2000;

async function withRetry(fn, retries = 2) {
  for (let i = 0; i <= retries; i++) {
    try {
      return await fn();
    } catch (err) {
      if (err.message === 'QUOTA_EXCEEDED') throw err; // Don't retry quota errors
      if (i === retries) throw err;
      console.warn(`  Retry ${i + 1} after error: ${err.message}`);
      await new Promise(r => setTimeout(r, RETRY_DELAY_MS * (i + 1)));
    }
  }
}

async function processBatch(paths, concurrency) {
  const results = [];
  const errors = [];

  // Process in batches to respect rate limits
  for (let i = 0; i < paths.length; i += concurrency) {
    const batch = paths.slice(i, i + concurrency);
    const settled = await Promise.allSettled(
      batch.map(p => withRetry(() => extractInvoice(p)))
    );
    settled.forEach((s, idx) => {
      if (s.status === 'fulfilled') results.push(s.value);
      else errors.push({ file: batch[idx], error: s.reason.message });
    });
    console.log(`  Processed ${Math.min(i + concurrency, paths.length)}/${paths.length}`);
  }

  return { results, errors };
}

function toCsv(invoices) {
  const headers = [
    '_source', 'invoice_number', 'date', 'vendor', 'vendor_gstin',
    'total', 'currency', 'tax_amount', 'subtotal'
  ];
  const rows = invoices.map(inv => headers.map(h => {
    const val = inv[h] ?? '';
    return typeof val === 'string' && val.includes(',') ? `"${val}"` : val;
  }).join(','));
  return [headers.join(','), ...rows].join('\n');
}

async function main() {
  mkdirSync(OUTPUT_DIR, { recursive: true });
  const paths = await glob(`${INPUT_DIR}/**/*.pdf`);

  if (paths.length === 0) {
    console.log('No PDF files found in', INPUT_DIR);
    return;
  }

  console.log(`Processing ${paths.length} invoices...`);
  const { results, errors } = await processBatch(paths, CONCURRENCY);

  // Write CSV
  if (results.length > 0) {
    const csvPath = join(OUTPUT_DIR, `invoices_${Date.now()}.csv`);
    writeFileSync(csvPath, toCsv(results));
    console.log(`\n✓ Wrote ${results.length} invoices to ${csvPath}`);
  }

  // Write JSON (full data including line items)
  if (results.length > 0) {
    const jsonPath = join(OUTPUT_DIR, `invoices_${Date.now()}.json`);
    writeFileSync(jsonPath, JSON.stringify(results, null, 2));
    console.log(`✓ Wrote full JSON to ${jsonPath}`);
  }

  // Report errors
  if (errors.length > 0) {
    console.error(`\n✗ Failed: ${errors.length} files`);
    errors.forEach(e => console.error(`  ${e.file}: ${e.error}`));
  }

  const total = results.reduce((sum, inv) => sum + (Number(inv.total) || 0), 0);
  console.log(`\nTotal invoice value: ${results[0]?.currency || 'USD'} ${total.toLocaleString()}`);
}

main().catch(console.error);

Run it:

node process.js ./invoices ./output
# Processing 24 invoices...
#   Processed 3/24
#   Processed 6/24
#   ...
#   Processed 24/24
# ✓ Wrote 24 invoices to ./output/invoices_1706700000000.csv
# ✓ Wrote full JSON to ./output/invoices_1706700000000.json
# Total invoice value: INR 8,47,500

What the AI extracts

The /ai/extract-invoice endpoint returns structured JSON for any invoice layout:

{
  "invoice_number": "INV-2024-1089",
  "date": "2024-11-28",
  "due_date": "2024-12-28",
  "vendor": "Mehta Electronics Pvt Ltd",
  "vendor_gstin": "27AADCM1234F1Z5",
  "buyer": "ABC Corp",
  "subtotal": 42500,
  "tax_amount": 7650,
  "total": 50150,
  "currency": "INR",
  "payment_terms": "Net 30",
  "line_items": [
    {
      "description": "Industrial UPS 5KVA",
      "quantity": 5,
      "unit_price": 8500,
      "amount": 42500,
      "hsn_code": "85044010"
    }
  ]
}

Adding a webhook for real-time notifications

If you want real-time notifications when invoices are processed (for a web app or Slack integration), set up a webhook in the API dashboard. The AllPDFMagic backend will POST a payload to your URL when each processing job completes.

// webhook-handler.js (Express route)
app.post('/webhook/invoice-processed', express.json(), (req, res) => {
  const { event, data } = req.body;
  if (event === 'result.completed') {
    console.log('Invoice processed:', data.invoice_number, data.total);
    // Update your database, send a Slack alert, etc.
  }
  res.json({ received: true });
});

Quota and cost

At 500 free calls/month (Starter tier), you can process ~500 invoices/month at no cost. The Indie tier ($9/mo) gives 2,000 calls — enough for most small businesses processing ~65 invoices/day.

Get your API key at allpdfmagic.com/dashboard/api.