fix: Correct comparison for typeof check.

[03eltond]

Requirements

• I have added test coverage for new or changed functionality
  *** I cannot validate tests execute due to following error during npm install:
  npm ERR! code E404
  npm ERR! 404 Not Found - GET https://registry.npmjs.org/@launchdarkly%2fprivate-js-mocks - Not found
  npm ERR! 404
  npm ERR! 404 '@launchdarkly/[email protected]' is not in the npm registry.
  npm ERR! 404 You should bug the author to publish it (or use the name yourself!)
  npm ERR! 404 It was specified as a dependency of 'sdk-server'
• I have followed the repository's pull request submission guidelines
• I have validated my changes against all supported platform versions

Describe the solution you've provided

This fixes the following error on Node.js v14:

ReferenceError: performance is not defined
at Migration.trackLatency (//node_modules/@launchdarkly/js-server-sdk-common/dist/Migration.js:245:13)

Since "undefined" !== undefined 😛

Additional context

The performance module is available in Node 14, however, it is not available globally until Node 16. An ideal fix may be to include an import of performance from perf_hooks - see https://stackoverflow.com/questions/46436943/referenceerror-performance-is-not-defined-when-using-performance-now

I originally wanted to add this in, but would be unable to validate that change due to npm install errors around a private package described above. Regardless, this fix appears to work using the existing fallback mechanism using Date objects.

[kinyoklion]

Thank you @03eltond

This change generally looks good, updated your title for conventional commits and made a suggestion for our prettier config.

This is intended, beyond node, to allow these checks in various edge environments as well (vercel, cloudflare, akamai). Which may have varying levels of support, so perf_hooks would be similarly problematic.

Thank you for finding this.

Thanks,
Ryan

[kinyoklion]

@03eltond @launchdarkly/[email protected] has been released this this change.

Thanks,
Ryan

[03eltond]

Thank you for the super fast turnaround!