@point-of-sale/webhid-barcode-scanner

WebHidBarcodeScanner

This is an library that allows you to use a Honeywell (and perhaps other manufacturers) barcode scanners in HID mode using WebHID.

This library is part of @point-of-sale, a collection of libraries for interfacing browsers and Node with Point of Sale devices such as receipt printers, barcode scanners and customer facing displays.

What does this library do?

By default most barcode scanners emulate a keyboard meaning all numbers and letters of a barcode will be individually 'typed' by the barscanner. This means you either have to focus an input field before scanning, or you have to use global keyboard events and build some algorithm that can seperate out digits from barcodes from other digits that are being typed on the keyboard.

This is error-prone and slow, but some barcode scanners can also be used in HID mode.

Depending on the model and manufacturer you might first need to scan a special configuration barcode to enable this mode. See the documentation of your barcode scanner for more information.

This library uses WebHID to connect to the scanner and set the scanner in HID mode, which allows us to receive the barcodes in one event.

How to use it?

Load the webhid-barcode-scanner.umd.js file in the browser and instantiate a WebHIDBarcodeScanner object.

<script src='webhid-barcode-scanner.umd.js'></script>

<script>

    const barcodeScanner = new WebHIDBarcodeScanner();

</script>

Or import the webhid-barcode-scanner.esm.js module:

import WebHIDBarcodeScanner from 'webhid-barcode-scanner.esm.js';

const barcodeScanner = new WebHIDBarcodeScanner();

Connect to a scanner

The first time you have to manually connect to the barcode scanner by calling the connect() function. This function must be called as the result of an user action, for example clicking a button. You cannot call this function on page load.

function handleConnectButtonClick() {
    barcodeScanner.connect();
}

Subsequent times you can simply call the reconnect() function. This will try to find any previously connected barcode scanners and will try to connect again. It is recommended to call this button on page load to prevent having to manually connect to a previously connected device.

barcodeScanner.reconnect();

If there are no barcode scanners connected that have been previously connected, this function will do nothing.

If you have multiple barcode scanners connected and want to reconnect with a specific one, you can provide an object with a vendor id and product id. You can get the vendor id and product id by listening to the connected event and store it for later use. Unfortunately this will only work for USB HID devices.

barcodeScanner.reconnect(lastUsedDevice);

However, this library will actively look for new devices being connected. So if you connect a previously connected barcode scanner, it will immediately become available.

To find out when a barcode scanner is connected you can listen for the connected event using the addEventListener() function.

barcodeScanner.addEventListener('connected', device => {
    console.log(`Connected to ${device.productName}`);

    /* Store device for reconnecting */
    lastUsedDevice = device;
});

The callback of the connected event is passed an object with the following properties:

• type
  Type of the connection that is used, in this case it is always hid.
• vendorId
  In case of a USB HID barcode scanner, the USB vendor ID.
• productId
  In case of a USB HID barcode scanner, the USB product ID.
• productName
  The name of the barcode scanner.

To find out when a barcode scanner is disconnected you can listen for the disconnected event using the addEventListener() function.

barcodeScanner.addEventListener('disconnected', () => {
    console.log(`Disconnected`);
});

Events

Once connected you can use listen for the following events to receive data from the barcode scanner.

Scanning barcodes

Whenever the libary detects a barcode, it will send out a barcode event that you can listen for.

barcodeScanner.addEventListener('barcode', e => {
    console.log(`Found barcode ${e.value} with symbology ${e.symbology}`);
});

The callback is passed an object with the following properties:

• value
  The value of the barcode as a string
• aim
  The AIM Code ID, which is a 3 character ISO/IEC identifier (originally created by AIM) generated by the decoder of a scanner and gives information about the symbology of the barcode which was scanned.
• symbology
  Optionally a library specific identifier of the symbology.

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This library has been created by Niels Leenheer under the MIT license. Feel free to use it in your products. The development of this library is sponsored by Salonhub.