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barcode-detector

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

Supported barcode formats: aztec, code_128, code_39, code_93, codabar, databar, databar_expanded, databar_limited, data_matrix, dx_film_edge, ean_13, ean_8, itf, maxi_code (only generated ones, and no position info), micro_qr_code, pdf417, qr_code, rm_qr_code, upc_a, upc_e, linear_codes and matrix_codes (for convenience).

Install

To install, run the following command:

npm i barcode-detector

Recommended Usage with Node + ESM

This package can be imported in three different ways:

Pure Module

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

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

import { BarcodeDetector as BarcodeDetectorPolyfill } from "barcode-detector/pure";

This approach is beneficial when you want to use a package to detect barcodes without polluting globalThis, or when your runtime already provides an implementation of the Barcode Detection API, but you still want this package to function.

Side Effects

import "barcode-detector/side-effects";

This approach is beneficial when you need a drop-in polyfill. If there's already an implementation of Barcode Detection API on globalThis, this won't take effect (type declarations will, as we cannot optionally declare types). In such cases, please use the pure module instead.

Both

import { BarcodeDetector } from "barcode-detector";

This approach combines the pure module and side effects.

Recommended Usage in Modern Browsers

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

  1. Include side effects:

    <!-- register -->
<script
  type="module"
  src="https://fastly.jsdelivr.net/npm/barcode-detector@2/dist/es/side-effects.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@2/dist/es/pure.min.js";
  const barcodeDetector = new BarcodeDetector();
</script>

  3. With import maps:

    <!-- import map -->
<script type="importmap">
  {
    "imports": {
      "barcode-detector/pure": "https://fastly.jsdelivr.net/npm/barcode-detector@2/dist/es/pure.min.js"
    }
  }
</script>

<!-- script scoped access -->
<script type="module">
  import { BarcodeDetector } from "barcode-detector/pure";
  const barcodeDetector = new BarcodeDetector();
</script>

Usage with Legacy Compatibility

Starting from v1.2, this package supports IIFE and CJS build outputs for use cases that require legacy compatibility.

IIFE

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

<!-- 
  IIFE pure.js registers:
  window.BarcodeDetectionAPI.BarcodeDetector
  window.BarcodeDetectionAPI.setZXingModuleOverrides
  -->
<script src="https://fastly.jsdelivr.net/npm/barcode-detector@2/dist/iife/pure.min.js"></script>

<!-- 
  IIFE side-effects.js registers:
  window.BarcodeDetector
  window.BarcodeDetectionAPI.setZXingModuleOverrides
  -->
<script src="https://fastly.jsdelivr.net/npm/barcode-detector@2/dist/iife/side-effects.min.js"></script>

<!-- 
  IIFE index.js registers:
  window.BarcodeDetector
  window.BarcodeDetectionAPI.BarcodeDetector
  window.BarcodeDetectionAPI.setZXingModuleOverrides
  -->
<script src="https://fastly.jsdelivr.net/npm/barcode-detector@2/dist/iife/index.min.js"></script>

CJS

This package can also be consumed as a commonjs package:

  1. Vanilla Javascript:

    // src/index.js
const { BarcodeDetector } = require("barcode-detector/pure");

  2. With Typescript:

    // src/index.ts
import { BarcodeDetector } from "barcode-detector/pure";

    tsconfig.json:

    {
  "compilerOptions": {
    "module": "CommonJS",
    "moduleResolution": "Node",
    "skipLibCheck": true
  },
  "include": ["src"]
}

setZXingModuleOverrides

In addition to BarcodeDetector, this package exports another function called setZXingModuleOverrides.

This package employs zxing-wasm to enable the core barcode reading functionality. As a result, a .wasm binary file is fetched at runtime. The default fetch path for this binary file is:

https://fastly.jsdelivr.net/npm/zxing-wasm@<version>/dist/reader/zxing_reader.wasm

The setZXingModuleOverrides function allows you to govern where the .wasm binary is served from, thereby enabling offline use of the package, use within a local network, or within a site having strict CSP rules.

For instance, should you want to inline this .wasm file in your build output for offline usage, with the assistance of build tools, you could try:

// src/index.ts
import wasmFile from "../node_modules/zxing-wasm/dist/reader/zxing_reader.wasm?url";

import {
  setZXingModuleOverrides,
  BarcodeDetector,
} from "barcode-detector/pure";

setZXingModuleOverrides({
  locateFile: (path, prefix) => {
    if (path.endsWith(".wasm")) {
      return wasmFile;
    }
    return prefix + path;
  },
});

const barcodeDetector = new BarcodeDetector();

// detect barcodes
// ...

Alternatively, the .wasm file could be copied to your dist folder to be served from your local server, without incorporating it into the output as an extensive base64 data URL.

It's noteworthy that you'll always want to choose the correct version of the .wasm file, so the APIs exported by it are exactly what the js code expects.

For more information on how to use this function, you can check the notes here and discussions here and here.

This function is exported from all the subpaths, including the side effects.

API

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

Lifecycle Events

The BarcodeDetector provided by this package also extends class EventTarget and provides 2 lifecycle events: load and error. You can use addEventListener and removeEventListener to register and remove callback hooks on these events.

load Event

The load event, which is a CustomEvent, will be dispatched on the successful instantiation of ZXing wasm module. For advanced usage, the instantiated module is passed as the detail parameter.

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

const barcodeDetector = new BarcodeDetector();

barcodeDetector.addEventListener("load", ({ detail }) => {
  console.log(detail); // zxing wasm module
});

error Event

The error event, which is a CustomEvent, will be dispatched if the instantiation of ZXing wasm module is failed. An error is passed as the detail parameter.

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

const barcodeDetector = new BarcodeDetector();

barcodeDetector.addEventListener("error", ({ detail }) => {
  console.log(detail); // an error
});

Example

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

const barcodeDetector: BarcodeDetector = new BarcodeDetector({
  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, as well as the build output, except for the parts listed below, is licensed under the MIT license.

Test samples and resources are collected from web-platform-tests/wpt, which is licensed under the 3-Clause BSD license.