mirror of
https://github.com/facebook/react-native.git
synced 2025-11-01 09:14:26 +00:00
Emilis Baliukonis
232517a574
Summary: When experimenting with React Profiler API (https://reactjs.org/docs/profiler.html), I noticed that durations are integers without a debugger, but they are doubles with higher precision when debugger is attached. After digging into React Profiler code, I found out that it's using `performance.now()` to accumulate execution times of individual units of work. Since this method does not exist in React Native, it falls back to Javascript `Date`, leading to imprecise results. This PR introduces `global.nativePerformanceNow` function which returns precise native time, and a very basic `performance` polyfill with `now` function. This will greatly improve React Profiler API results, which is essential for profiling and benchmark tools. Solves https://github.com/facebook/react-native/issues/27274 ## Changelog [General] [Added] - Implement `nativePerformanceNow` and `performance.now()` Pull Request resolved: https://github.com/facebook/react-native/pull/27885 Test Plan: ``` const initialTime = global.performance.now(); setTimeout(() => { const newTime = global.performance.now(); console.warn('duration', newTime - initialTime); }, 1000); ``` ### Android + Hermes  ### Android + JSC  ### iOS  Reviewed By: ejanzer Differential Revision: D19888289 Pulled By: rickhanlonii fbshipit-source-id: ab8152382da9aee9b4b3c76f096e45d40f55da6c
