fix(core): use typeof check in isEvent to prevent ReferenceError in non-browser runtimes

[leifarriens]

Problem

Error tracking in posthog-react-native is non-functional. When initializing PostHog with error tracking autocapture enabled:

new PostHog("phc_", {
  errorTracking: {
    autocapture: {
      console: [],
      uncaughtExceptions: true,
      unhandledRejections: true,
    },
  },
});

No $exception events are ever sent. The isEvent() utility in @posthog/core directly references the Event global, which doesn't exist in React Native's Hermes runtime. The resulting error surfaces as:

ERROR [PostHog] [ErrorTracking] An error occurred while capturing an $exception event: [ReferenceError: Property 'Event' doesn't exist]

Changes

• Use typeof Event !== 'undefined' instead of !isUndefined(Event) in isEvent() to safely handle runtimes where Event doesn't exist.
• Added tests for isEvent().

Release info Sub-libraries affected

Libraries affected

• All of them
• posthog-js (web)
• posthog-js-lite (web lite)
• posthog-node
• posthog-react-native
• @posthog/react
• @posthog/ai
• @posthog/convex
• @posthog/next
• @posthog/nextjs-config
• @posthog/nuxt
• @posthog/rollup-plugin
• @posthog/webpack-plugin
• @posthog/types

Checklist

• Tests for new code
• Accounted for the impact of any changes across different platforms
• Accounted for backwards compatibility of any changes (no breaking changes!)
• Took care not to unnecessarily increase the bundle size

If releasing new changes

• Ran pnpm changeset to generate a changeset file
• Added the "release" label to the PR to indicate we're publishing new versions for the affected packages

[vercel]

@leifarriens is attempting to deploy a commit to the PostHog Team on Vercel.

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[greptile-apps]

Prompt To Fix All With AI

This is a comment left during a code review.
Path: packages/core/src/utils/type-utils.spec.ts
Line: 34-38

Comment:
**Test can silently pass without asserting**

The `if (typeof Event !== 'undefined')` guard means this test will pass vacuously in any environment where `Event` is not defined (e.g., a Node.js test runner without jsdom). No assertion is ever executed and the test reports success while actually verifying nothing.

Consider using `it.skipIf` (Vitest) or a similar mechanism to make the skip explicit and visible:

```
it.skipIf(typeof Event === 'undefined')('returns true for Event instances when Event global exists', () => {
  expect(isEvent(new Event('test'))).toBe(true)
})
```

Or, if the test environment is always jsdom (where `Event` is defined), remove the guard entirely since it's never needed.

How can I resolve this? If you propose a fix, please make it concise.

---

This is a comment left during a code review.
Path: packages/core/src/utils/type-utils.spec.ts
Line: 40-46

Comment:
**Prefer parameterised test**

The existing tests in this file use `it.each` for parameterised cases (see `isNumber` and `isPositiveNumber`). This test checks multiple non-Event values individually — it should follow the same pattern for consistency:

```suggestion
    it.each([
      [new Error('test'), false],
      ['string', false],
      [{}, false],
      [null, false],
      [undefined, false],
    ])('isEvent(%p) returns %p', (value, expected) => {
      expect(isEvent(value)).toBe(expected)
    })
```

How can I resolve this? If you propose a fix, please make it concise.

_{Last reviewed commit: "fix(core): use typeo..."}

[greptile-apps]

Test can silently pass without asserting

The if (typeof Event !== 'undefined') guard means this test will pass vacuously in any environment where Event is not defined (e.g., a Node.js test runner without jsdom). No assertion is ever executed and the test reports success while actually verifying nothing.

Consider using it.skipIf (Vitest) or a similar mechanism to make the skip explicit and visible:

it.skipIf(typeof Event === 'undefined')('returns true for Event instances when Event global exists', () => {
  expect(isEvent(new Event('test'))).toBe(true)
})

Or, if the test environment is always jsdom (where Event is defined), remove the guard entirely since it's never needed.

Prompt To Fix With AI

This is a comment left during a code review.
Path: packages/core/src/utils/type-utils.spec.ts
Line: 34-38

Comment:
**Test can silently pass without asserting**

The `if (typeof Event !== 'undefined')` guard means this test will pass vacuously in any environment where `Event` is not defined (e.g., a Node.js test runner without jsdom). No assertion is ever executed and the test reports success while actually verifying nothing.

Consider using `it.skipIf` (Vitest) or a similar mechanism to make the skip explicit and visible:

```
it.skipIf(typeof Event === 'undefined')('returns true for Event instances when Event global exists', () => {
  expect(isEvent(new Event('test'))).toBe(true)
})
```

Or, if the test environment is always jsdom (where `Event` is defined), remove the guard entirely since it's never needed.

How can I resolve this? If you propose a fix, please make it concise.

[greptile-apps]

Prefer parameterised test

The existing tests in this file use it.each for parameterised cases (see isNumber and isPositiveNumber). This test checks multiple non-Event values individually — it should follow the same pattern for consistency:

Suggested change

	it('returns false for non-Event values', () => {
	expect(isEvent(new Error('test'))).toBe(false)
	expect(isEvent('string')).toBe(false)
	expect(isEvent({})).toBe(false)
	expect(isEvent(null)).toBe(false)
	expect(isEvent(undefined)).toBe(false)
	})
	it.each([
	[new Error('test'), false],
	['string', false],
	[{}, false],
	[null, false],
	[undefined, false],
	])('isEvent(%p) returns %p', (value, expected) => {
	expect(isEvent(value)).toBe(expected)
	})

Prompt To Fix With AI

This is a comment left during a code review.
Path: packages/core/src/utils/type-utils.spec.ts
Line: 40-46

Comment:
**Prefer parameterised test**

The existing tests in this file use `it.each` for parameterised cases (see `isNumber` and `isPositiveNumber`). This test checks multiple non-Event values individually — it should follow the same pattern for consistency:

```suggestion
    it.each([
      [new Error('test'), false],
      ['string', false],
      [{}, false],
      [null, false],
      [undefined, false],
    ])('isEvent(%p) returns %p', (value, expected) => {
      expect(isEvent(value)).toBe(expected)
    })
```

How can I resolve this? If you propose a fix, please make it concise.

_{Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!}