Node.js / receipts
Receipt PDFs in Node.js
Post your receipt HTML to a render API from a route handler that returns the response body directly, then pipe the response body straight to res, so the PDF never lands in a Buffer. No browser binary in your Node.js deployment.
Why receipts become PDFs
A receipt is proof a payment happened, and customers attach it to expense claims. It has to survive being forwarded, printed and filed by someone who never had an account with you. That is the difference between a document and a view of a database, and it is why ecommerce and point-of-sale teams keep asking for this.
What a receipt has to carry
Before any of the code below matters, the template has to produce a document that is actually a receipt. These are the fields that make it one, and the ones a reader or an auditor will look for first.
- the payment reference from the processor, which is what a dispute is traced by
- the amount actually captured, which is not always the amount ordered
- the payment method, usually the card brand and last four digits
- the timestamp with a timezone, since expense systems reconcile by date
- the merchant legal name, which may differ from the brand on the site
The Node.js implementation
fetch ships with the runtime, so this adds no dependency. The render happens in a route handler that returns the response body directly, and you pipe the response body straight to res, so the PDF never lands in a Buffer.
javascript
app.get("/receipt/:id.pdf", async (req, res) => {
const html = await renderReceipt(req.params.id);
const upstream = await fetch("https://api.pdfpipe.xyz/v1/pdf", {
method: "POST",
headers: {
Authorization: `Bearer ${process.env.PDFPIPE_KEY}`,
"Content-Type": "application/json",
},
body: JSON.stringify({
html,
options: { format: "A4", printBackground: true },
}),
});
if (!upstream.ok) throw new Error(`render failed: ${upstream.status}`);
res.setHeader("Content-Type", "application/pdf");
// Streamed, not buffered: a long receipt never sits in memory.
upstream.body.pipe(res);
});The CSS that makes a receipt page correctly
The layout problem specific to this document is that receipts are short and usually want a narrow page, so the default A4 canvas leaves an expanse of white unless the page size is set deliberately. These rules handle it.
css
/* A receipt on A4 is mostly white space. Set the page to the
content, and let it grow only as far as the items require. */
@page {
size: 80mm 200mm;
margin: 6mm;
}
body { font-size: 11px; }What goes wrong in Node.js
Node buffers the whole response if you call res.send(await res.arrayBuffer()). On a 40-page report that is tens of megabytes held per concurrent request, and it is the usual reason a PDF endpoint takes down an otherwise healthy service under load.
What people try first
Most Node.js projects reach for puppeteer, which pulls a 300 MB Chromium download into your image and needs its own memory headroom on every instance. That works until it is running on more than one machine, at which point the browser becomes the thing you operate rather than the thing you use.
Where the receipt lives afterwards
Rendering is the short part. The customer keeps it, not you, and they submit it to an expense system months later. It has to be readable by software that never saw your site, which is why the amount and reference belong in selectable text rather than inside an image.
Getting the document right
- Check the amount paid and the payment reference, which is what an expense system matches against.
- Generation is triggered by a successful payment webhook, so size the timeout for that path rather than for a health check.
- Volume arrives in bursts, so queue the render rather than doing it inside the request that triggered it.
- Backgrounds are painted by default here, so a design that uses colour needs nothing set. Only an explicit print_background of false turns them off.
Frequently asked
Do I need Chromium installed to generate receipts from Node.js?
No. The render happens over HTTP, so your Node.js deployment stays the size it is now. That is the main reason to use an API rather than puppeteer, which pulls a 300 MB Chromium download into your image and needs its own memory headroom on every instance.
How do I stop a long receipt using all the memory?
Pipe the response body straight to res, so the PDF never lands in a Buffer. Node buffers the whole response if you call res.send(await res.arrayBuffer()). On a 40-page report that is tens of megabytes held per concurrent request, and it is the usual reason a PDF endpoint takes down an otherwise healthy service under load.
What has to be on a receipt?
At minimum: the payment reference from the processor, which is what a dispute is traced by; the amount actually captured, which is not always the amount ordered; the payment method, usually the card brand and last four digits. The one to get right before anything else is the amount paid and the payment reference, which is what an expense system matches against.
Do I need to store the generated receipts?
Depends on the document, and this one has a clear answer: the customer keeps it, not you, and they submit it to an expense system months later. It has to be readable by software that never saw your site, which is why the amount and reference belong in selectable text rather than inside an image.
Can I keep my existing receipt template?
Yes, if it produces HTML. Whatever renders your receipt view today can render the same markup for the PDF, which is why the CSS above is the only new thing you write.
Related
Other Node.js documents, and the same receipt in other stacks.
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