ReceiptPrinterEncoder

ReceiptPrinterEncoder (formerly known as EscPosEncoder, StarPrntEncoder, and ThermalPrinterEncoder) is a library used to generate command sets for receipt printers. It allows you to define content such as text, images, and barcodes, and then encodes that content into commands compatible with printers supporting ESC/POS, StarLine, or StarPRNT protocols.

Note that this library only handles the encoding of commands. To actually print the receipt, you must use a separate library (part of the @point-of-sale collection) to send the resulting encoded data to the physical printer hardware.

To make a cell cover more than one column, use an object instead of a string or callback for the cell value. This is useful for headers or totals.

Properties for Spanned Cells:

• content: The actual content (string or callback).
• span: The number of columns to cover (default is 1).
• align: Overrides the column's horizontal alignment.
• border: Can turn off the table's borders for this specific cell (none or specific sides like { left: 'none' }).
• marginLeft / marginRight: Overrides the column's margins.

Constraint: The sum of all span values in a row must exactly equal the total number of columns defined in the table configuration.

// Example of a cell spanning 2 columns in a 3-column table
[
    [ 'Beer', '2', '13.00' ],
    [ { span: 2, content: 'Total', align: 'right' }, '185.80' ]
]

Receipt printers do not support Unicode or UTF-8. Instead, they rely on legacy code pages to represent different character sets.

To print text correctly, you must ensure the printer supports the specific code page you intend to use. Support varies significantly by manufacturer and model. Always consult your printer's technical manual before selecting a code page. If a printer lacks hardware support for a specific character set, the library cannot force it to print correctly.

Lists in markdown() are treated as tables with a marker column and a fill column. This ensures that wrapped lines of an item hang under the text rather than under the marker.

List Types

• Unordered Lists: Use -, *, or +. The marker printed is always -.
• Ordered Lists: Use 1. item or 1) item. The list counts from the number of its first item.
• Nesting: Indent items by two or more spaces per level to create nested lists. Nested lists maintain their own numbering.

Layout

• The marker column width is determined by the widest marker in the list plus one space.
• If the marker column is too narrow to allow text, items are printed as simple lines of text with the marker and a space.

- Meals and goods at the reduced tax rate
  - Coffee and tea
- Paid in cash
1. Keep this receipt
2. Visit [our site](https://example.com)

The library requires structuredClone(), which is missing in React Native and the Hermes engine. To prevent the error Property 'structuredClone' doesn't exist, you must install and polyfill it in your application's entry point before importing the encoder.

1. Install the polyfill:

npm install @ungap/structured-clone

2. Apply the polyfill globally:

import structuredClone from '@ungap/structured-clone';

if (typeof globalThis.structuredClone !== 'function') {
    globalThis.structuredClone = structuredClone;
}

Note on Images: The image() function requires a way to read pixels. Ensure you provide the appropriate input types or use the createCanvas option as described in the image command documentation.

While there is no dedicated deno.land/x package, the library is fully compatible with Deno. You can import it directly from the NPM registry using the npm: specifier.

import ReceiptPrinterEncoder from 'npm:@point-of-sale/receipt-printer-encoder';

let encoder = new ReceiptPrinterEncoder();

The easiest way to configure the library is by specifying a printerModel. This automatically sets important options like language, supported code pages, and imageMode.

If your specific model is not listed, you can try a similar model or use generic models like pos-5890 or pos-8360 for many unbranded printers. For cheap Bluetooth 'cat' or 'meow' printers that only support image printing, use the meow model.

You can view all supported models via the ReceiptPrinterEncoder.printerModels static property.

let encoder = new ReceiptPrinterEncoder({
    printerModel: 'epson-tm-t88vi'
});

When working in a Node.js environment, use one of the following sister libraries to transmit the encoded data to your printer:

• NetworkReceiptPrinter: Use this to print directly to a printer over a network (e.g., via TCP/IP).
• SystemReceiptPrinter: Use this to print to a printer that is already installed and managed by your operating system.

First, install the package via npm:

npm install @point-of-sale/receipt-printer-encoder --save

Then, you can use it with either ES6 modules or CommonJS:

ES6 Modules:

import ReceiptPrinterEncoder from '@point-of-sale/receipt-printer-encoder';
const encoder = new ReceiptPrinterEncoder();

CommonJS:

const ReceiptPrinterEncoder = require('@point-of-sale/receipt-printer-encoder');
const encoder = new ReceiptPrinterEncoder();