refactor: add cross-environment decodeBase64 method

.github/workflows/ci.yml

@@ -12,7 +12,8 @@ jobs:
       matrix:
         node-version:
           - 18
-          - '*'
+          - 25 # Node.js 25 support Uint8Array.fromBase64()
+          - 'lts/*'
     steps:
       - uses: actions/checkout@v6
       - uses: actions/setup-node@v6

globals.d.ts

@@ -0,0 +1,61 @@
+// Adapted from file://./node_modules/typescript/lib/lib.dom.d.ts so we don't have to include the entire DOM lib
+// Ref: https://github.com/microsoft/TypeScript/issues/31535, https://github.com/microsoft/TypeScript/issues/41727, https://github.com/microsoft/TypeScript-DOM-lib-generator/issues/1685
+
+/** [MDN Reference](https://developer.mozilla.org/docs/Web/API/Window/atob) */
+declare function atob(data: string): string;
+/** [MDN Reference](https://developer.mozilla.org/docs/Web/API/Window/btoa) */
+declare function btoa(data: string): string;
+
+type AllowSharedBufferSource =
+  | ArrayBufferLike
+  | ArrayBufferView<ArrayBufferLike>;
+
+interface TextDecodeOptions {
+  stream?: boolean;
+}
+
+interface TextDecoderOptions {
+  fatal?: boolean;
+  ignoreBOM?: boolean;
+}
+
+/**
+ * The **`TextDecoder`** interface represents a decoder for a specific text encoding, such as `UTF-8`, `ISO-8859-2`, `KOI8-R`, `GBK`, etc.
+ *
+ * [MDN Reference](https://developer.mozilla.org/docs/Web/API/TextDecoder)
+ */
+interface TextDecoder extends TextDecoderCommon {
+  /**
+   * The **`TextDecoder.decode()`** method returns a string containing text decoded from the buffer passed as a parameter.
+   *
+   * [MDN Reference](https://developer.mozilla.org/docs/Web/API/TextDecoder/decode)
+   */
+  decode(input?: AllowSharedBufferSource, options?: TextDecodeOptions): string;
+}
+
+// eslint-disable-next-line no-var
+declare var TextDecoder: {
+  prototype: TextDecoder;
+  new (label?: string, options?: TextDecoderOptions): TextDecoder;
+};
+
+interface TextDecoderCommon {
+  /**
+   * Returns encoding's name, lowercased.
+   *
+   * [MDN Reference](https://developer.mozilla.org/docs/Web/API/TextDecoder/encoding)
+   */
+  readonly encoding: string;
+  /**
+   * Returns true if error mode is "fatal", otherwise false.
+   *
+   * [MDN Reference](https://developer.mozilla.org/docs/Web/API/TextDecoder/fatal)
+   */
+  readonly fatal: boolean;
+  /**
+   * Returns the value of ignore BOM.
+   *
+   * [MDN Reference](https://developer.mozilla.org/docs/Web/API/TextDecoder/ignoreBOM)
+   */
+  readonly ignoreBOM: boolean;
+}

package.json

@@ -27,7 +27,6 @@
   },
   "devDependencies": {
     "@borderless/ts-scripts": "^0.15.0",
-    "@types/node": "^20.19.35",
     "@vitest/coverage-v8": "^3.2.4",
     "typescript": "^5.9.3",
     "vitest": "^3.2.4"

src/index.ts

@@ -6,8 +6,6 @@
  * MIT Licensed
  */
 
-import { Buffer } from 'node:buffer';
-
 export = auth;
 
 /**
@@ -101,14 +99,45 @@ const CREDENTIALS_REGEXP =
 
 const USER_PASS_REGEXP = /^([^:]*):(.*)$/;
 
+type Uint8ArrayWithBase64 = typeof Uint8Array & {
+  fromBase64?: (str: string) => Uint8Array;
+};
+
+type BufferLike = {
+  from(
+    input: string,
+    encoding: 'base64',
+  ): { toString(encoding: 'utf-8'): string };
+};
+
+const NodeBuffer = (globalThis as any).Buffer as BufferLike | undefined;
+
+const textDecoder = new TextDecoder('utf-8');
+
 /**
  * Decode base64 string.
  * @private
  */
+const decodeBase64: (str: string) => string = (() => {
+  // 1) Modern Web / some runtimes
+  if (typeof (Uint8Array as Uint8ArrayWithBase64).fromBase64 === 'function') {
+    return (str: string) =>
+      textDecoder.decode((Uint8Array as Uint8ArrayWithBase64).fromBase64!(str));
+  }
 
-function decodeBase64(str: string): string {
-  return Buffer.from(str, 'base64').toString();
-}
+  // 2) Node.js (fast path)
+  if (typeof NodeBuffer?.from === 'function') {
+    return (str: string) => NodeBuffer.from(str, 'base64').toString('utf-8');
+  }
+
+  // 3) Browser fallback
+  return (str: string) => {
+    const binary = atob(str);
+    return textDecoder.decode(
+      Uint8Array.from(binary, (char) => char.charCodeAt(0)),
+    );
+  };
+})();
 
 /**
  * Get the Authorization header from request object.

tsconfig.json

@@ -7,7 +7,7 @@
     "outDir": "dist",
     "module": "nodenext",
     "moduleResolution": "nodenext",
-    "types": ["node"]
+    "types": ["./globals.d.ts"]
   },
   "include": ["src/**/*"]
 }