Barcode Scanner

It is a simple utility inspired by simple-barcode-scanner but made as a native and global keyboard scanner driver for Deno, this means that it doesn’t depend on any browser and it listens even when no GUI/UI/TERMINAL (stdin) is focused.

Most barcode scanners act like a keyboard, Barcode Scanner handles this by listening for native events without using the DOM API. This is useful for scanning without focusing on any screen and works for multiple devices.

Why?

I needed a way to use multiple scanners on a PC without depending on one window being focused. It is not viable / reliable to use on GUIs and browser running on machines used by several users at time.

Don’t be scare! Barcode Scanner is pretty simple too and it can be used with a single scanner on a simple app :D, but with the security that data is not getting lost anymore.

How?

Barcode scanners are HID devices also, but there’s one trick, they are FORBIDEN by some systems… Basically they doesn’t allow HID connections for keyboards and mouses for security reasons. So while looking for a solution I found that it is not that useful and we can’t take a direct connection from the device.

So, how it is native?: We use GKM to capture native/global keys and keybindings events. This is because neither Node or Deno support native events for keyboards and mouses. Anyway, it is incredibly fast as well.

📦 Import

import BarcodeScanner from "https://deno.land/x/barcode_scanner@1.0.0/mod.ts";

🖥️ Usage

You can use NBS as a global listener or as a dedicated device listener.

Basic (global):

This will listen to all devices and will catch all codes from the multiple emitting devices. This is the way if you have just one device or if your device doesn’t allow prefixing.

import BarcodeScanner from "./mod.ts";

const options = {...foo}

const scanner = new BarcodeScanner(options);

// Add a global listener

for await (const code of scanner.reader()) {
  console.log(code)
}

// Stop the listener
scanner.off();

Dedicated device:

As I said before, some devices allow code prefixing functions and you can use it to scope the NBS events.

To do this, you have to prefix your device with your chosen device ID string and then specify it at options.devicePrefix.

Note: NBS doesn’t prefix your device, you must use one that does. Please read your device user guide.

import BarcodeScanner from "./mod.ts";

const options = {
  devicePrefix: 'id1'
}

const scanner = new BarcodeScanner(options);

// Add a global device scoped listener
for await (const code of scanner.reader()) {
  // This only works for the device(s) prefixed with id
  console.log(code)
}
// Remove the listener
scanner.off();

Note: We un-prefix the code for you ;) you can log it as clean as it is on the paper.

EventEmitter API deprecation

Please note that node and browser versións uses an EventEmitter like API, it is deprecated now and we are aiming the usage of Deno’s way. It is compatible just with the deno stream API, out of the box. If you want to use it as before (with the events API) you must see the next example:

import Readable from 'https://deno.land/std@0.99.0/node/_stream/readable.ts';
import BarcodeScanner from '../mod.ts'

const scanner = Readable.from(new BarcodeScanner({
  endKeys: ['Intro', 'Enter']
}).reader());

scanner.on('data', (code: string) => {
  console.log(code)
});

🧰 API

BarcodeScanner

Creates an instance of Scanner to use the code events.

Parameters

Options? Object
- latency Number Max time duration (in ms) between consecutive inputs
  
  default: 50
- minLength Number Min length of a valid barcode
  
  default: 3
- endKeys string | Array Key name indicating end of barcode
  
  Refer Key Values | MDN
  
  default: ["Return"]
- validKey RegExp Regular expression to check for a valid key in barcode
  
  Refer Key Values | MDN
  
  default: /^\w$/
- devicePrefix string Prefix ID for device scoped events
  
  _default: null
Please note: options.endKeys is always “Return”, if you know that your device or one of them have a different endKey, you must add those endKeys into the array. Eg: ['L', 'F1', ...].

Returns Scanner

Scanner

reader Async iterator: Starts listening for barcode scans.

_yields: Event Object
off Function: Stop listening for barcode scans and remove the listener. _returns: void

🌐 Using on web and node

Please if you are on browser use simple-barcode-scanner

If you want the multi-device update use my fork @denyncrawford/simple-barcode-scanner

Please check native-barcode-scanner for using in node.

🔥 Spam

This modules uses GKM: If you want to listen global input events, go check it out!.

👥 Credits

Developer: denyncrawford

This idea couln’t be possible without simple-barcode-scanner, thanks.

🏗️ Contributing

Create an issue related to the problem or idea and check if it is viable
Fork it :D
Create a new branch with your changes.
Make a PR.

📜 License

MIT License

See full licese