thermal-printer-lib

Thermal Printer Library

A set of useful utilities for working with ip thermal printers.

Provides abstractions for creating prop-driven, reusable presets and components and discovering printers on a network.

Uses the node-thermal-printer library for buffer creation and printing.

You can get a reference to the underlying node-thermal-printer instance by calling the getPrinter method.

Basic usage

---

Prints "Hello world" to a local thermal printer using the ReceiptText component.

const instance = new PrinterInstance('192.168.1.10');

await instance.connect();

instance.apply([
  new ReceiptText({
    align: 'center',
    bold: true,
    text: 'Hello world',
  }),
]);

await instance.flush(true, true, true);

The flush method provides optional parameters for cut, open cash drawer and beep. (if available)

All components are fully typed so their props can be easily inspected.

• Basket *
• Custom
• Cut
• Footer
• Hr
• LeftRight
• Meta *
• Qr
• Text
• Title *
• Vat-Number *

* composed of other components

Usage with buffers

---

Creates an instance that stores the buffer to be printed later.

const bufferOnlyInstance = new PrinterInstance();

bufferOnlyInstance.apply([
  new ReceiptText({
    align: 'center',
    bold: true,
    text: 'Hello world',
  }),
]);

const encodedBuffer = bufferOnlyInstance.getBase64EncodedBuffer();

// then you can pass this string to a connected instance later to be printed

const instance = new PrinterInstance('192.168.1.10');

await instance.connect();

instance.addBase64EncodedBuffer(encodedBuffer);

await instance.flush();

Using the node-thermal-printer instance

---

Access the underlying instance by calling the getPrinter method.

The packages printer interface is re-exported as ThermalPrinter.

const instance = new PrinterInstance();

const printer: ThermalPrinter = instance.getPrinter();

// same output as the `ReceiptText` component in the above example
printer.alignTextCenter();
printer.bold(true);
printer.printLn('Hello world');
printer.bold(false);
printer.alignTextLeft();

Custom components

---

A component is a simple way to abstract code that may be called many times across receipts. A few basic components are provided for you but you can create custom ones for your own use case.

When applied the components apply method is called passing it the current instance.

A component should always reset any changes it's applied.

class ReceiptBoldText extends PrinterComponentBase {
  constructor(private text: string) {}

  apply(instance: PrinterInstance) {
    const printer = instance.getPrinter();

    printer.bold(true);
    printer.printLn(this.text);
    printer.bold(false);
  }
}

// now can be applied like so
instance.apply(new ReceiptBoldText('Hello world'));

Custom presets

---

A preset is just a pure function that returns an array of components.

interface SimpleReceiptPresetProps {
  items: string[];
}

function simpleEposReceiptPreset(props: SimpleReceiptPresetProps) {
  return [
    new ReceiptTitle({
      locationName: 'Test Shop',
      locationAddress: '1 Demo Street, Town, XX12 XXX',
      servedBy: 'Tom',
    }),
    ...items.map(item => new ReceiptText({ text: item })),
    new ReceiptFooter({
      customerCopy: false,
    }),
    // you can also use the `ReceiptCustom` component here
    new ReceiptCustom((instance: PrinterInstance) => {
      const printer: ThermalPrinter = instance.getPrinter();

      printer.printLn('custom line');
    }),
  ];
}

const result = simpleEposReceiptPreset({ items: ['Item one', 'Item two'] });

// apply the result to the instance
instance.apply(result);

The createEncodedBufferFromPreset function handles instance creation and returns a base64 encoded string.

Discover network printers

---

Easily search for printers on a network by providing an ip, subnet or ip-range.

const discovered = await discoverPrinters('192.168.1.0/24');

discovered.forEach(discoveredPrinter => {
  console.log(discoveredPrinter);
});

// > { ip: '192.168.1.10', mac: "...", latency: 12 }
// > { ip: '192.168.1.11', mac: "...", latency: 114 }
// > { ip: '192.168.1.12', mac: "...", latency: 67 }

There are also a few other helpful network utilities provided:

• checkRemotePortOpen

(address: string, port?: number, timeout?: number) => Promise<boolean>

• getIpFromMacAddress

(mac: string, searchAddress?: string) => Promise<string>

• checkPrinterConnection

(ip: string, mac: string, port?: number, timeout?: number) => Promise<boolean>