@shopify/flash-list
Version:
FlashList is a more performant FlatList replacement
60 lines • 2.31 kB
JavaScript
import { ErrorMessages } from "../errors/ErrorMessages";
import { roundToDecimalPlaces } from "./roundToDecimalPlaces";
/**
* Can be used to monitor JS thread performance
* Use startTracking() and stopAndGetData() to start and stop tracking
*/
export class JSFPSMonitor {
constructor() {
this.startTime = 0;
this.frameCount = 0;
this.timeWindow = {
frameCount: 0,
startTime: 0,
};
this.minFPS = Number.MAX_SAFE_INTEGER;
this.maxFPS = 0;
this.averageFPS = 0;
this.clearAnimationNumber = 0;
this.updateLoopCompute = () => {
this.frameCount++;
const elapsedTime = (Date.now() - this.startTime) / 1000;
this.averageFPS = elapsedTime > 0 ? this.frameCount / elapsedTime : 0;
this.timeWindow.frameCount++;
const timeWindowElapsedTime = (Date.now() - this.timeWindow.startTime) / 1000;
if (timeWindowElapsedTime >= 1) {
const timeWindowAverageFPS = this.timeWindow.frameCount / timeWindowElapsedTime;
this.minFPS = Math.min(this.minFPS, timeWindowAverageFPS);
this.maxFPS = Math.max(this.maxFPS, timeWindowAverageFPS);
this.timeWindow.frameCount = 0;
this.timeWindow.startTime = Date.now();
}
this.measureLoop();
};
}
measureLoop() {
// This looks weird but I'm avoiding a new closure
this.clearAnimationNumber = requestAnimationFrame(this.updateLoopCompute);
}
startTracking() {
if (this.startTime !== 0) {
throw new Error(ErrorMessages.fpsMonitorAlreadyRunning);
}
this.startTime = Date.now();
this.timeWindow.startTime = Date.now();
this.measureLoop();
}
stopAndGetData() {
cancelAnimationFrame(this.clearAnimationNumber);
if (this.minFPS === Number.MAX_SAFE_INTEGER) {
this.minFPS = this.averageFPS;
this.maxFPS = this.averageFPS;
}
return {
minFPS: roundToDecimalPlaces(this.minFPS, 1),
maxFPS: roundToDecimalPlaces(this.maxFPS, 1),
averageFPS: roundToDecimalPlaces(this.averageFPS, 1),
};
}
}
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