get Buffer and atob/btoa from global object explicitly

Author: lobsterkatie

packages/utils/src/string.ts

@@ -104,6 +104,14 @@ export function isMatchingPattern(value: string, pattern: RegExp | string): bool
   return false;
 }
 
+type GlobalWithBase64Helpers = {
+  // browser
+  atob?: (base64String: string) => string;
+  btoa?: (utf8String: string) => string;
+  // Node
+  Buffer?: { from: (input: string, encoding: string) => { toString: (encoding: string) => string } };
+};
+
 /**
  * Convert a Unicode string to a base64 string.
  *
@@ -112,26 +120,30 @@ export function isMatchingPattern(value: string, pattern: RegExp | string): bool
  * @returns A base64-encoded version of the string
  */
 export function unicodeToBase64(plaintext: string): string {
-  const global = getGlobalObject();
+  const globalObject = getGlobalObject() as GlobalWithBase64Helpers;
 
   // To account for the fact that different platforms use different character encodings natively, our `tracestate`
   // spec calls for all jsonified data to be encoded in UTF-8 bytes before being passed to the base64 encoder.
   try {
     // browser
-    if ('btoa' in global) {
+    if ('btoa' in globalObject) {
       // encode using UTF-8
       const bytes = new TextEncoder().encode(plaintext);
 
       // decode using UTF-16 (JS's native encoding) since `btoa` requires string input
       const bytesAsString = String.fromCharCode(...bytes);
 
-      return btoa(bytesAsString);
+      // TODO: if TS ever learns about "in", we can get rid of the non-null assertion
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      return globalObject.btoa!(bytesAsString);
     }
 
     // Node
-    if ('Buffer' in global) {
+    if ('Buffer' in globalObject) {
       // encode using UTF-8
-      const bytes = Buffer.from(plaintext, 'utf-8');
+      // TODO: if TS ever learns about "in", we can get rid of the non-null assertion
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      const bytes = globalObject.Buffer!.from(plaintext, 'utf-8');
 
       // unlike the browser, Node can go straight from bytes to base64
       return bytes.toString('base64');
@@ -157,7 +169,7 @@ export function unicodeToBase64(plaintext: string): string {
  * @returns A Unicode string
  */
 export function base64ToUnicode(base64String: string): string {
-  const globalObject = getGlobalObject();
+  const globalObject = getGlobalObject() as GlobalWithBase64Helpers;
 
   // To account for the fact that different platforms use different character encodings natively, our `tracestate` spec
   // calls for all jsonified data to be encoded in UTF-8 bytes before being passed to the base64 encoder. So to reverse
@@ -166,7 +178,9 @@ export function base64ToUnicode(base64String: string): string {
     // browser
     if ('atob' in globalObject) {
       // `atob` returns a string rather than bytes, so we first need to encode using the native encoding (UTF-16)
-      const bytesAsString = atob(base64String);
+      // TODO: if TS ever learns about "in", we can get rid of the non-null assertion
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      const bytesAsString = globalObject.atob!(base64String);
       const bytes = [...bytesAsString].map(char => char.charCodeAt(0));
 
       // decode using UTF-8 (cast the `bytes` arry to a Uint8Array just because that's the format `decode()` expects)
@@ -176,7 +190,9 @@ export function base64ToUnicode(base64String: string): string {
     // Node
     if ('Buffer' in globalObject) {
       // unlike the browser, Node can go straight from base64 to bytes
-      const bytes = Buffer.from(base64String, 'base64');
+      // TODO: if TS ever learns about "in", we can get rid of the non-null assertion
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      const bytes = globalObject.Buffer!.from(base64String, 'base64');
 
       // decode using UTF-8
       return bytes.toString('utf-8');