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

The guide

1. 1

   No install needed for Node 18+

   Node.js 18 has fetch, FormData and Blob built in.

2. 2

   Set your API key as an environment variable

   Never put the key in client-side code:

   export DOCUPARSE_API_KEY="dex_your_key_here"

3. 3

   Submit the file and fetch the result

   POST the file to /api/v1/extract, then poll GET /api/v1/documents/{id} until the status is completed. On Starter and Pro you can skip polling: add a webhook in Dashboard → Settings and DocuParse API will POST the finished result to your endpoint.

   const API = "https://docuparseapi.com/api/v1";
   const headers = { Authorization: `Bearer ${process.env.DOCUPARSE_API_KEY}` };
   
   async function parseDocument(fileBuffer, fileName) {
     // 1. Submit
     const form = new FormData();
     form.append("file", new Blob([fileBuffer]), fileName);
     const submit = await fetch(`${API}/extract`, { method: "POST", headers, body: form }).then((r) => r.json());
     if (!submit.success) throw new Error(`[${submit.error.code}] ${submit.error.message}`);
   
     // 2. Fetch the result
     for (let i = 0; i < 40; i++) {
       const doc = await fetch(`${API}/documents/${submit.document_id}`, { headers }).then((r) => r.json());
       if (doc.status === "completed") return doc.data;
       if (doc.status === "failed") throw new Error(`Extraction failed: ${submit.document_id}`);
       await new Promise((r) => setTimeout(r, 1500));
     }
     throw new Error(`Timed out: ${submit.document_id}`);
   }
   
   const data = await parseDocument(require("fs").readFileSync("invoice.pdf"), "invoice.pdf");
   console.log(data.merchant, data.total, data.currency);

   Need your API key first?

   20 free documents/month — no credit card

   Sign up — get a free API key
4. 4

   Read the JSON result

   Access fields directly on the fetched data object — no post-processing needed:

   const data = await parseDocument(require("fs").readFileSync("invoice.pdf"), "invoice.pdf");
   console.log(data.merchant);
   console.log(data.total);
   console.log(data.currency);
   console.log(data.line_items); // description, quantity, price, line_total, vat_rate

5. 5

   Add a server-side proxy for browser apps

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

   // app/api/documents/parse/route.ts — keeps your API key on the server
   import { NextRequest, NextResponse } from "next/server";
   
   const API = "https://docuparseapi.com/api/v1";
   const headers = { Authorization: `Bearer ${process.env.DOCUPARSE_API_KEY}` };
   
   export async function POST(request: NextRequest) {
     const incoming = await request.formData();
     const upstream = new FormData();
     upstream.append("file", incoming.get("file") as File);
   
     const submit = await fetch(`${API}/extract`, { method: "POST", headers, body: upstream }).then((r) => r.json());
     if (!submit.success) return NextResponse.json(submit, { status: 400 });
   
     // Return the id now; the client polls GET /api/documents/[id] (which calls
     // GET ${API}/documents/{id}), or use a webhook on Starter and Pro.
     return NextResponse.json({ document_id: submit.document_id, status: submit.status });
   }

Full working example

const API = "https://docuparseapi.com/api/v1";
const headers = { Authorization: `Bearer ${process.env.DOCUPARSE_API_KEY}` };

async function parseDocument(fileBuffer, fileName) {
  // 1. Submit
  const form = new FormData();
  form.append("file", new Blob([fileBuffer]), fileName);
  const submit = await fetch(`${API}/extract`, { method: "POST", headers, body: form }).then((r) => r.json());
  if (!submit.success) throw new Error(`[${submit.error.code}] ${submit.error.message}`);

  // 2. Fetch the result
  for (let i = 0; i < 40; i++) {
    const doc = await fetch(`${API}/documents/${submit.document_id}`, { headers }).then((r) => r.json());
    if (doc.status === "completed") return doc.data;
    if (doc.status === "failed") throw new Error(`Extraction failed: ${submit.document_id}`);
    await new Promise((r) => setTimeout(r, 1500));
  }
  throw new Error(`Timed out: ${submit.document_id}`);
}

const data = await parseDocument(require("fs").readFileSync("invoice.pdf"), "invoice.pdf");
console.log(data.merchant, data.total, data.currency);