@callstack/reassure-measure/lib/commonjs/polyfills.js

Performance measurement library for React and React Native

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.applyRenderPolyfills = applyRenderPolyfills;
exports.revertRenderPolyfills = revertRenderPolyfills;
var _perf_hooks = require("perf_hooks");
var _testingLibrary = require("./testing-library");
function applyRenderPolyfills() {
  const testingLibrary = (0, _testingLibrary.getTestingLibrary)();
  if (testingLibrary === 'react-native') {
    polyfillPerformanceNow();
  }
}
function revertRenderPolyfills() {
  const testingLibrary = (0, _testingLibrary.getTestingLibrary)();
  if (testingLibrary === 'react-native') {
    restorePerformanceNow();
  }
}

/**
 * React Native Jest preset mocks the global.performance object, with `now()` method being `Date.now()`.
 * Ref: https://github.com/facebook/react-native/blob/3dfe22bd27429a43b4648c597b71f7965f31ca65/packages/react-native/jest/setup.js#L41
 *
 * Then React uses `performance.now()` in `Scheduler` to measure component render time.
 * https://github.com/facebook/react/blob/45804af18d589fd2c181f3b020f07661c46b73ea/packages/scheduler/src/forks/Scheduler.js#L59
 */
let originalPerformanceNow;
function polyfillPerformanceNow() {
  originalPerformanceNow = global.performance?.now;
  global.performance.now = () => _perf_hooks.performance.now();
}
function restorePerformanceNow() {
  globalThis.performance.now = originalPerformanceNow;
}
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