barcode-detector

A Barcode Detection API ponyfill/polyfill that uses ZXing-C++ WebAssembly under the hood.

Supported barcode formats:

Linear Barcode Formats	Matrix Barcode Formats	Special Barcode Formats
codabar	aztec	linear_codes1
code_39	data_matrix	matrix_codes2
code_93	maxi_code3	any4
code_128	pdf417
databar	qr_code
databar_limited	micro_qr_code
databar_expanded	rm_qr_code
dx_film_edge
ean_8
ean_13
itf
upc_a
upc_e

Install

To install, run the following command:

npm i barcode-detector

Usage

Ponyfill

import { BarcodeDetector } from "barcode-detector/ponyfill";

To avoid potential namespace collisions, you can also rename the export:

import { BarcodeDetector as BarcodeDetectorPonyfill } from "barcode-detector/ponyfill";

A ponyfill is a module required to be explicitly imported without introducing side effects. Use this subpath if you want to avoid polluting the global object with the BarcodeDetector class, or if you intend to use the implementation provided by this package instead of the native one.

Polyfill

import "barcode-detector/polyfill";

This subpath is used to polyfill the native BarcodeDetector class. It will automatically register the BarcodeDetector class in the global object if it's not already present.

Important

The polyfill will opt in only if no BarcodeDetector is present in globalThis. It basically works like this:

import { BarcodeDetector } from "barcode-detector/ponyfill";
globalThis.BarcodeDetector ??= BarcodeDetector;

Note that it doesn't check if the implementation is provided natively or by another polyfill. It also doesn't try to augment the existing implementation with all the barcode formats supported by this package. If you want all the features provided by this package, but you already have a native or another polyfilled BarcodeDetector, you should use the ponyfill approach. You can register it to the globalThis object manually if you want to.

Ponyfill + Polyfill

import { BarcodeDetector } from "barcode-detector";

This approach combines the ponyfill and polyfill approaches.

Note

The ponyfill subpath was named pure and the polyfill subpath was named side-effects in early versions. They are no longer recommended for use and are considered deprecated. Please use the new subpaths as described above.

<script type="module">

For modern browsers that support ES modules, this package can be imported via the <script type="module"> tags:

1. Include the polyfill:

   <!-- register -->
   <script
     type="module"
     src="https://fastly.jsdelivr.net/npm/barcode-detector@3/dist/es/polyfill.min.js"
   ></script>
   
   <!-- use -->
   <script type="module">
     const barcodeDetector = new BarcodeDetector();
   </script>

2. Script scoped access:

   <script type="module">
     import { BarcodeDetector } from "https://fastly.jsdelivr.net/npm/barcode-detector@3/dist/es/ponyfill.min.js";
     const barcodeDetector = new BarcodeDetector();
   </script>

3. With import maps:

   <!-- import map -->
   <script type="importmap">
     {
       "imports": {
         "barcode-detector/ponyfill": "https://fastly.jsdelivr.net/npm/barcode-detector@3/dist/es/ponyfill.min.js"
       }
     }
   </script>
   
   <!-- script scoped access -->
   <script type="module">
     import { BarcodeDetector } from "barcode-detector/ponyfill";
     const barcodeDetector = new BarcodeDetector();
   </script>

IIFE

For legacy browsers or userscripts that lack support for <script type="module"> tags, IIFE is the preferred choice. Upon executing the IIFE script, a variable named BarcodeDetectionAPI will be registered in the global window by var declaration.

<!-- 
  IIFE ponyfill.js registers:
  window.BarcodeDetectionAPI.BarcodeDetector
  window.BarcodeDetectionAPI.prepareZXingModule
  -->
<script src="https://fastly.jsdelivr.net/npm/barcode-detector@3/dist/iife/ponyfill.min.js"></script>

<!-- 
  IIFE polyfill.js registers:
  window.BarcodeDetector
  window.BarcodeDetectionAPI.prepareZXingModule
  -->
<script src="https://fastly.jsdelivr.net/npm/barcode-detector@3/dist/iife/polyfill.min.js"></script>

<!-- 
  IIFE index.js registers:
  window.BarcodeDetector
  window.BarcodeDetectionAPI.BarcodeDetector
  window.BarcodeDetectionAPI.prepareZXingModule
  -->
<script src="https://fastly.jsdelivr.net/npm/barcode-detector@3/dist/iife/index.min.js"></script>

prepareZXingModule

The core barcode reading functionality of this package is powered by zxing-wasm. Therefore, a .wasm binary file is fetched at runtime. By default, the .wasm serving path is initialized with a jsDelivr CDN URL. However, there're cases where this is not desired, such as the allowed serving path is white-listed by the Content Security Policy (CSP), or offline usage is required.

To customize the .wasm serving path, this package reexports prepareZXingModule along with ZXING_WASM_VERSION and ZXING_WASM_SHA256 from zxing-wasm. For more details on how to use them, please check Configuring .wasm Serving and Controlling .wasm Instantiation Timing and Caching sections in the zxing-wasm repository.

An example usage to override the .wasm serving path with an unpkg.com CDN url is as follows:

import {
  BarcodeDetector,
  ZXING_WASM_VERSION,
  prepareZXingModule,
} from "barcode-detector/ponyfill";

// Override the locateFile function
prepareZXingModule({
  overrides: {
    locateFile: (path, prefix) => {
      if (path.endsWith(".wasm")) {
        return `https://unpkg.com/zxing-wasm@${ZXING_WASM_VERSION}/dist/reader/${path}`;
      }
      return prefix + path;
    },
  },
});

// Now you can create a BarcodeDetector instance
const barcodeDetector = new BarcodeDetector({
  formats: ["qr_code"],
});

Note

The setZXingModuleOverrides method is deprecated in favor of prepareZXingModule.

API

Please check the spec, MDN doc and Chromium implementation for more information.

An example usage is as follows:

import { BarcodeDetector } from "barcode-detector/ponyfill";

// check supported formats
const supportedFormats = await BarcodeDetector.getSupportedFormats();

const barcodeDetector: BarcodeDetector = new BarcodeDetector({
  // make sure the formats are supported
  formats: ["qr_code"],
});

const imageFile = await fetch(
  "https://api.qrserver.com/v1/create-qr-code/?size=150x150&data=Hello%20world!",
).then((resp) => resp.blob());

barcodeDetector.detect(imageFile).then(console.log);

License

The source code in this repository is licensed under the MIT license.

Footnotes

1. linear_codes is a shorthand for all linear barcode formats. ↩

2. matrix_codes is a shorthand for all matrix barcode formats. ↩

3. Detection support for MaxiCode requires a pure monochrome image that contains an unrotated and unskewed symbol, along with a sufficient white border surrounding it. ↩

4. any is a shorthand for linear_codes and matrix_codes, i.e., all barcode formats. Note that you don't need to specify any in the formats option, as not providing the option also indicates detecting all barcode formats. ↩