Invoice Parsing in Node.js — Receipt & Invoice Extraction for JavaScript Apps

One POST request. Clean JSON back. Works in Express, Next.js, or any Node.js environment.

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✓ Free DocuParseAPI account✓ Node 18+✓ Server runtime

The guide

No install needed for Node 18+

Node.js 18 has fetch built in. For older versions only:

npm install node-fetch form-data

Set your API key as an environment variable

Never put the key in client-side code:

export DOCUPARSE_API_KEY="dex_your_key_here"

Send the file using FormData

Read the file buffer, create a Blob, append to FormData, POST to the extract endpoint:

const fs = require("fs");
const path = require("path");

async function parseInvoice(filePath) {
  const fileBuffer = fs.readFileSync(filePath);
  const blob = new Blob([fileBuffer]);
  const form = new FormData();
  form.append("file", blob, path.basename(filePath));

  const response = await fetch("https://docuparseapi.com/api/v1/extract", {
    method: "POST",
    headers: { Authorization: `Bearer ${process.env.DOCUPARSE_API_KEY}` },
    body: form,
  });

  const data = await response.json();
  if (!data.success) throw new Error(`[${data.error.code}]`);
  return data;
}

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Read the JSON response

Access fields directly — no post-processing needed:

const invoice = await parseInvoice('invoice.pdf');
console.log(invoice.merchant);  // 'Acme Corp'
console.log(invoice.total);     // '1320.00'
console.log(invoice.currency);  // 'USD'
console.log(invoice.line_items); // array of items

Add a server-side proxy for browser apps

Never call the DocuParseAPI from browser JavaScript — your key would be exposed. Use a Next.js API route to proxy the request:

// app/api/invoices/upload/route.ts
import { NextRequest, NextResponse } from "next/server";

export async function POST(request: NextRequest) {
  const formData = await request.formData();
  const file = formData.get("file") as File;

  const upstream = new FormData();
  upstream.append("file", file);

  const response = await fetch("https://docuparseapi.com/api/v1/extract", {
    method: "POST",
    headers: { Authorization: `Bearer ${process.env.DOCUPARSE_API_KEY}` },
    body: upstream,
  });

  return NextResponse.json(await response.json());
}

Full working example

javascript

const fs = require("fs");
const path = require("path");

async function parseInvoice(filePath) {
  const fileBuffer = fs.readFileSync(filePath);
  const blob = new Blob([fileBuffer]);
  const form = new FormData();
  form.append("file", blob, path.basename(filePath));

  const response = await fetch("https://docuparseapi.com/api/v1/extract", {
    method: "POST",
    headers: { Authorization: `Bearer ${process.env.DOCUPARSE_API_KEY}` },
    body: form,
  });

  const data = await response.json();
  if (!data.success) throw new Error(`[${data.error.code}] ${data.error.message}`);
  return data;
}

const invoice = await parseInvoice("invoice.pdf");
console.log(`${invoice.merchant}: ${invoice.currency} ${invoice.total}`);
for (const item of invoice.line_items || []) {
  console.log(`  ${item.description}: ${item.quantity} x ${item.unit_price}`);
}

What gets extracted

merchantThe vendor or store name

totalThe final charged amount including tax

subtotalThe pre-tax amount

taxThe tax amount charged

dateInvoice or transaction date (ISO 8601)

due_datePayment due date, or null if not present

invoice_idInvoice number or receipt ID from the document

currencyISO 4217 currency code (USD, EUR, GBP, etc.)

payment_methodCard type, cash, or other payment method

line_itemsArray of items with description, quantity, unit_price, total

Common errors and fixes

MISSING_API_KEYAuthorization header missingAdd header: Authorization: Bearer YOUR_KEY

INVALID_API_KEYKey not recognisedCheck key in dashboard — regenerate if needed

LIMIT_EXCEEDEDMonthly document limit reachedUpgrade at docuparseapi.com/pricing

UNSUPPORTED_FILE_TYPEFile format not supportedUse PDF, JPG, or PNG only

FILE_TOO_LARGE_AUTHENTICATEDFile exceeds 10 MBCompress the file before sending

EXTRACTION_FAILEDDocument could not be parsedTry a cleaner scan or different file

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