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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
27 lines
617 B
JavaScript
27 lines
617 B
JavaScript
/**
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @flow strict-local
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* @format
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*/
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'use strict';
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if (!global.performance) {
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global.performance = {};
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}
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/**
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* Returns a double, measured in milliseconds.
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* https://developer.mozilla.org/en-US/docs/Web/API/Performance/now
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*/
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if (typeof global.performance.now !== 'function') {
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global.performance.now = function() {
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const performanceNow = global.nativePerformanceNow || Date.now;
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return performanceNow();
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};
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}
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