Split base64 utilities to avoid browser polyfills.

Separate base64ToBytes implementation into Node.js and browser-specific files to prevent static analyzers from injecting unnecessary Buffer polyfills into browser bundles. Add browser field aliasing to package.json for automatic environment-specific loading.

Changes:
- Create lib/util.js with Node.js implementation using Buffer.
- Create lib/utilBrowser.js with browser implementation using atob.
- Add browser field to package.json for file aliasing.
- Update nfcRenderer.js to import from util.js (bundler handles switching).
- Remove inline _base64ToBytes function from nfcRenderer.js.
- Rename dataUri to dataUrl throughout for consistency.
- Update error messages to use 'data URL' instead of 'data URI'.
- Update test assertions to match new error messages.

Author: bparth24

lib/nfcRenderer.js

@@ -9,6 +9,7 @@
  */
 import * as base58 from 'base58-universal';
 import * as base64url from 'base64url-universal';
+import {base64ToBytes} from './util.js';
 
 const multibaseDecoders = new Map([
   ['u', base64url],
@@ -269,9 +270,9 @@ async function _decodeTemplateToBytes({renderMethod, filteredData} = {}) {
 }
 
 async function _decodeTemplate({encoded} = {}) {
-  // data URI format
+  // data URL format
   if(encoded.startsWith('data:')) {
-    return _decodeDataUri({dataUri: encoded});
+    return _decodeDataUrl({dataUrl: encoded});
   }
 
   // multibase format (base58 'z' or base64url 'u')
@@ -281,7 +282,7 @@ async function _decodeTemplate({encoded} = {}) {
 
   throw new Error(
     'Unknown template encoding format. ' +
-    'Supported formats: data URI (data:...) or multibase (z..., u...)'
+    'Supported formats: data URL (data:...) or multibase (z..., u...)'
   );
 }
 
@@ -290,20 +291,20 @@ async function _decodeTemplate({encoded} = {}) {
 // ========================
 
 /**
- * Decode a data URI to bytes.
+ * Decode a data URL to bytes.
  * Validates media type is application/octet-stream..
  *
  * @private
  * @param {object} options - Options object.
- * @param {string} options.dataUri - Data URI string.
+ * @param {string} options.dataUrl - Data URL string.
  * @returns {Uint8Array} Decoded bytes.
- * @throws {Error} If data URI is invalid or has wrong media type.
+ * @throws {Error} If data URL is invalid or has wrong media type.
  */
-function _decodeDataUri({dataUri} = {}) {
-  // parse data URI format: data:mime/type;encoding,data
-  const match = dataUri.match(/^data:([^;]+);([^,]+),(.*)$/);
+function _decodeDataUrl({dataUrl} = {}) {
+  // parse data URL format: data:mime/type;encoding,data
+  const match = dataUrl.match(/^data:([^;]+);([^,]+),(.*)$/);
   if(!match) {
-    throw new Error('Invalid data URI format.');
+    throw new Error('Invalid data URL format.');
   }
 
   const mimeType = match[1];
@@ -313,20 +314,20 @@ function _decodeDataUri({dataUri} = {}) {
   // validate media type is application/octet-stream
   if(mimeType !== 'application/octet-stream') {
     throw new Error(
-      'Invalid data URI media type. ' +
+      'Invalid data URL media type. ' +
       'NFC templates must use "application/octet-stream" media type. ' +
       `Found: "${mimeType}"`
     );
   }
 
   // decode based on encoding
   if(encoding === 'base64') {
-    return _base64ToBytes({base64String: data});
+    return base64ToBytes({base64String: data});
   }
   if(encoding === 'base64url') {
     return base64url.decode(data);
   }
-  throw new Error(`Unsupported data URI encoding: ${encoding}`);
+  throw new Error(`Unsupported data URL encoding: ${encoding}`);
 }
 
 /**
@@ -349,29 +350,6 @@ function _decodeMultibase({input} = {}) {
   return decoder.decode(encodedData);
 }
 
-/**
- * Decode standard base64 to bytes.
- *
- * @private
- * @param {object} options - Options object.
- * @param {string} options.base64String - Base64 encoded string.
- * @returns {Uint8Array} Decoded bytes.
- */
-function _base64ToBytes({base64String} = {}) {
-  // use atob in browser, Buffer in Node
-  if(typeof atob !== 'undefined') {
-    const binaryString = atob(base64String);
-    const bytes = new Uint8Array(binaryString.length);
-    for(let i = 0; i < binaryString.length; i++) {
-      bytes[i] = binaryString.charCodeAt(i);
-    }
-    return bytes;
-  }
-
-  // Node.js environment
-  return Buffer.from(base64String, 'base64');
-}
-
 // ========================
 // JSON pointer utilities
 // ========================

lib/util.js

@@ -0,0 +1,25 @@
+/*!
+ * Copyright (c) 2025 Digital Bazaar, Inc. All rights reserved.
+ */
+
+/**
+ * Decode base64 string to bytes (Node.js implmentation).
+ *
+ * @param {object} options - Options object.
+ * @param {string} options.base64String - Base64 encoded string.
+ * @returns {Uint8Array} Decoded bytes.
+ */
+export function base64ToBytes({base64String} = {}) {
+  return new Uint8Array(Buffer.from(base64String, 'base64'));
+}
+
+/**
+ * Encode bytes to base64 string (Node.js implementation).
+ *
+ * @param {object} options - Options object.
+ * @param {Uint8Array} options.bytes - Bytes to encode.
+ * @returns {string} Base64 encoded string.
+ */
+export function bytesToBase64({bytes} = {}) {
+  return Buffer.from(bytes).toString('base64');
+}

lib/utilBrowser.js

@@ -0,0 +1,46 @@
+/*!
+ * Copyright (c) 2025 Digital Bazaar, Inc. All rights reserved.
+ */
+
+/**
+ * Decode base64 string to bytes (Browser implmentation).
+ *
+ * @param {object} options - Options object.
+ * @param {string} options.base64String - Base64 encoded string.
+ * @returns {Uint8Array} Decoded bytes.
+ */
+export function base64ToBytes({base64String} = {}) {
+  // Use modern API
+  if(typeof Uint8Array.fromBase64 === 'function') {
+    return Uint8Array.fromBase64(base64String);
+  }
+
+  // Fallback to atob
+  const binaryString = atob(base64String);
+  const bytes = new Uint8Array(binaryString.length);
+  for(let i = 0; i < binaryString.length; i++) {
+    bytes[i] = binaryString.charCodeAt(i);
+  }
+  return bytes;
+}
+
+/**
+ * Encode bytes to base64 string (Browser implementation).
+ *
+ * @param {object} options - Options object.
+ * @param {Uint8Array} options.bytes - Bytes to encode.
+ * @returns {string} Base64 encoded string.
+ */
+export function bytesToBase64({bytes} = {}) {
+  // Use modern API
+  if(typeof Uint8Array.prototype.toBase64 === 'function') {
+    return bytes.toBase64();
+  }
+
+  // Fallback to btoa
+  let binaryString = '';
+  for(let i = 0; i < bytes.length; i++) {
+    binaryString += String.fromCharCode(bytes[i]);
+  }
+  return btoa(binaryString);
+}

package.json

@@ -4,6 +4,9 @@
   "description": "Bedrock Web Wallet",
   "type": "module",
   "exports": "./lib/index.js",
+  "browser": {
+    "./lib/util.js": "./lib/utilBrowser.js"
+  },
   "files": [
     "lib/*"
   ],