TypeScript timer/timing utilities for conveniently profiling code, for example to record the time taken by various function sections

Timer.ts

export class Timer {
  private static nextTimerIndex = 0;

  public readonly timerIndex;
  private startTime: number | undefined;
  private endTime: number | undefined;

  constructor(startOnInit: boolean = false) {
    this.timerIndex = Timer.nextTimerIndex++;
    if (startOnInit) this.start();
  }

  private static getCurrentTime() {
    return Date.now();
  }

  start() {
    if (this.startTime !== undefined) {
      throw new Error("Timer has already been started");
    }
    this.startTime = Timer.getCurrentTime();
  }

  stop() {
    if (this.startTime === undefined) {
      throw new Error("Timer has not yet been started");
    } // intentionally silent on repeat stops
    this.endTime = Timer.getCurrentTime();
  }

  getRecordedTime() {
    if (this.startTime == undefined || this.endTime === undefined) {
      throw new Error("Timer has not recorded a time");
    }
    return this.endTime - this.startTime;
  }
}

TimerGroup.ts

export class TimerGroup {
  private readonly timers: Map<string, Timer> = new Map();

  registerTimer(timerName: string) {
    this.timers.set(timerName, new Timer(false));
  }

  startTimer(timerName: string) {
    if (this.timers.has(timerName)) {
      this.timers.get(timerName)!.start();
    } else {
      this.timers.set(timerName, new Timer(true));
    }
  }

  stopTimer(timerName: string) {
    if (this.timers.has(timerName)) {
      this.timers.get(timerName)!.stop();
    } // silent
  }

  stopAllTimers() {
    this.timers.forEach(timer => timer.stop());
  }

  summarize() { // console.log return value of this for quick summary of timers
    Array.from(this.timers.keys()).forEach(timerName => {
      const timer = this.timers.get(timerName)!;
      return `${timerName} (${timer.timerIndex}): ${timer.getRecordedTime()}ms`;
    });
  }
}