bysquare

v3.0.0

Published

9 days ago

It's a national standard for payment QR codes adopted by Slovak Banking Association (SBA)

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xseman

pay by square qr string paybysquare bysquare

Why

It's simple, I couldn't find any implementation of "PAY by square" standard for JavaScript, so I decided to create one and share it with the community to help individuals and businesses to create QR codes for their invoices.

Features

TypeScript support
Compatible with Slovak banking apps
Isomorphic Browser & Runtime-independent implementation

Installation

npm

$ npm install bysquare

browser

<script type="module">
	import { encode, decode } from "https://esm.sh/bysquare@latest";
</script>

Quick start

This library provides encode and decode functions to work with the data model directly, allowing you to create customized payment solutions.

Guides

HTML example

This example shows how to generate a payment QR code and display it in a web page:

<!DOCTYPE html>
<html lang="en">
	<head>
		<meta charset="UTF-8" />
		<title>Payment QR Code</title>
	</head>
	<body>
		<div id="qrcode" style="width: 200px"></div>

		<script type="module">
			import { QRCode } from "https://esm.sh/@lostinbrittany/qr-esm@latest";
			import { encode, PaymentOptions, CurrencyCode } from "https://esm.sh/bysquare@latest";

			const qrstring = encode({
				payments: [
					{
						type: PaymentOptions.PaymentOrder,
						amount: 123.45,
						variableSymbol: "987654",
						currencyCode: CurrencyCode.EUR,
						bankAccounts: [
							{ iban: "SK9611000000002918599669" }
						],
					},
				],
			});

			const qrElement = document.getElementById("qrcode");
			qrElement.appendChild(QRCode.generateSVG(qrstring));
		</script>
	</body>
</html>

Creating Payment QR Codes

To generate QR codes for different payment types, use the encode function with the appropriate payment configuration:

import {
	CurrencyCode,
	encode,
	PaymentOptions,
	Periodicity,
} from "bysquare";

// Simple Payment (Payment Order)
const qrstring = encode({
	payments: [
		{
			type: PaymentOptions.PaymentOrder, // 1
			amount: 50.75,
			variableSymbol: "123456",
			currencyCode: CurrencyCode.EUR, // "EUR"
			bankAccounts: [
				{ iban: "SK9611000000002918599669" },
			],
		},
	],
});

// Standing Order
const qrstring = encode({
	payments: [
		{
			type: PaymentOptions.StandingOrder, // 3
			amount: 100.0,
			variableSymbol: "654321",
			currencyCode: CurrencyCode.EUR, // "EUR"
			day: 15,
			month: Month.January, // Single month
			periodicity: Periodicity.Monthly, // "m"
			bankAccounts: [
				{ iban: "SK9611000000002918599669" },
			],
		},
	],
});

// Direct Debit
const qrstring = encode({
	payments: [
		{
			type: PaymentOptions.DirectDebit, // 2
			amount: 25.0,
			variableSymbol: "789012",
			currencyCode: CurrencyCode.EUR, // "EUR"
			bankAccounts: [
				{ iban: "SK9611000000002918599669" },
			],
		},
	],
});

Standing Order with Multiple Months

For standing orders that should execute in specific months, you can combine multiple months using bitwise OR operators:

import {
	CurrencyCode,
	encode,
	encodeOptions,
	Month,
	PaymentOptions,
	Periodicity,
} from "bysquare";

const qrstring = encode({
	payments: [
		{
			type: PaymentOptions.StandingOrder,
			amount: 100.0,
			variableSymbol: "654321",
			currencyCode: CurrencyCode.EUR,
			day: 15,
			// Execute in January, July, and October only
			month: Month.January | Month.July | Month.October, // Results in 577
			periodicity: Periodicity.Monthly,
			lastDate: "20251231",
			bankAccounts: [
				{ iban: "SK9611000000002918599669" },
			],
		},
	],
});

// Alternative: Use the utility function to encode multiple months
const monthsToEncode = [Month.January, Month.July, Month.October];
const encodedMonths = encodeOptions(monthsToEncode);

const qrstring2 = encode({
	payments: [
		{
			type: PaymentOptions.StandingOrder,
			amount: 100.0,
			variableSymbol: "654321",
			currencyCode: CurrencyCode.EUR,
			day: 15,
			month: encodedMonths, // Same result: 577
			periodicity: Periodicity.Monthly,
			lastDate: "20251231",
			bankAccounts: [
				{ iban: "SK9611000000002918599669" },
			],
		},
	],
});

[!NOTE] Date Format: Provide date inputs (e.g., paymentDueDate, lastDate) in ISO 8601 format (YYYY-MM-DD). They are automatically converted to YYYYMMDD during encoding to match the Pay by Square specification.

Advanced usage

For more complex data with multiple payments and additional fields:

[!NOTE] Encoded data are without diacritics
The library removes all diacritics from the input data to ensure maximum compatibility, as not all banks support diacritics, which may lead to errors. If you need to retain diacritics, disable deburr option when encoding data - encode(model, { deburr: false }).

import {
	CurrencyCode,
	DataModel,
	decode,
	encode,
	PaymentOptions,
} from "bysquare";

const data = {
	invoiceId: "random-id",
	payments: [
		{
			type: PaymentOptions.PaymentOrder,
			currencyCode: CurrencyCode.EUR,
			amount: 100.0,
			variableSymbol: "123",
			paymentNote: "hello world",
			bankAccounts: [
				{ iban: "SK9611000000002918599669" },
				// ...more bank accounts
			],
			// ...more fields
		},
		// ...more payments
	],
} satisfies DataModel;

// Encode data to a QR string
const qrstring = encode(data);

// Decode QR string back to the original data model
const model = decode(qrstring);

Classifier Utilities

The library provides utility functions for working with multiple classifier options as specified in the PAY by Square standard. These functions are particularly useful for handling multiple month selections in standing orders.

Encoding Multiple Options

import {
	encodeOptions,
	Month,
} from "bysquare";

// Encode multiple months into a single value
const monthsArray = [Month.January, Month.July, Month.October];
const encoded = encodeOptions(monthsArray);
console.log(encoded); // 577 (1 + 64 + 512)

// This matches the specification example:
// January=1, July=64, October=512, sum=577

CLI

$ npm install --global bysquare

Encode

Encode JSON or JSONL data from files and print the corresponding QR code.

$ bysquare --encode file1.json file2.json...
$ bysquare --encode file.jsonl

Decode

Decode the specified QR code string and print the corresponding JSON data. The qrstring argument should be a valid QR code string.

$ bysquare --decode <qrstring>

How it works

Data Flow

Encoding/Decoding Architecture

Validation

This library uses permissive validation to ensure maximum compatibility with various Slovak banking applications. The validation does not strictly enforce all XSD schema restrictions.

Validation Behavior

| Aspect | Behavior | | ------------- | --------------------------------------------------------------- | | IBAN | Validated (format + checksum via ISO 13616) | | BIC | Validated (format via ISO 9362) | | Currency | Validated (ISO 4217, case-insensitive, includes XXX) | | Date | Validated (ISO 8601 format) | | Symbols | Permissive (accepts letters, spaces - XSD pattern not enforced) | | Amounts | Permissive (accepts negative values) | | Field lengths | Not enforced |

XSD Field Constraints Reference

https://www.bsqr.co/schema/

For reference, the official XSD schema defines these constraints (not enforced by this library):

| Field | Max Length | Pattern | | --------------------------------- | ---------- | ------------- | | variableSymbol | 10 | [0-9]{0,10} | | constantSymbol | 4 | [0-9]{0,4} | | specificSymbol | 10 | [0-9]{0,10} | | paymentNote | 140 | - | | originatorsReferenceInformation | 35 | - | | invoiceId | 10 | - | | beneficiary.name | 70 | - | | beneficiary.street | 70 | - | | beneficiary.city | 70 | - | | mandateId | 35 | - | | creditorId | 35 | - | | contractId | 35 | - | | amount | 15 | >= 0 |