device.ts: add edgecase test and refactor

Author: clairep94

client/utils/device.test.ts

@@ -26,4 +26,20 @@ describe('isMac', () => {
     });
     expect(isMac()).toBe(false);
   });
+
+  it('returns false when navigator agent is null', () => {
+    Object.defineProperty(navigator, 'userAgent', {
+      value: null,
+      configurable: true
+    });
+    expect(isMac()).toBe(false);
+  });
+
+  it('returns false when navigator agent is undefined', () => {
+    Object.defineProperty(navigator, 'userAgent', {
+      value: undefined,
+      configurable: true
+    });
+    expect(isMac()).toBe(false);
+  });
 });

client/utils/device.ts

@@ -1 +1,10 @@
-export const isMac = () => navigator.userAgent.toLowerCase().indexOf('mac') !== -1; // eslint-disable-line
+/**
+ * Checks if the user's OS is macOS based on the user agent string.
+ * This is the preferred method over navigator.platform, which is now deprecated:
+ *   - see https://developer.mozilla.org/en-US/docs/Web/API/Navigator/platform
+ */
+export function isMac(): boolean {
+  return typeof navigator?.userAgent === 'string'
+    ? navigator.userAgent.toLowerCase().includes('mac')
+    : false;
+}