Created a stopwatch class

Stopwatch.ts

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+//typescriptClasses/Stopwatch.ts
+//Matthew Ellison
+// Created: 10-18-20
+//Modified: 10-18-20
+//This file contains a class that is used to time the execution time of other programs
+/*
+Copyright (C) 2020  Matthew Ellison
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU Lesser General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU Lesser General Public License for more details.
+
+	You should have received a copy of the GNU Lesser General Public License
+	along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+
+import {InvalidResult} from "./InvalidResult";
+import {performance} from "perf_hooks";
+
+
+//An enum that helps keep track of how many times the time has been reduced in the getStr function
+enum TIME_RESOLUTION{ NANOSECOND, MICROSECOND, MILLISECOND, SECOND, MINUTE, HOUR, ERROR };
+
+export class Stopwatch{
+	private startTime: number;
+	private stopTime: number;
+	//Constructor makes sure all values are set to defaults
+	public constructor(){
+		//Make sure both values are null so it is easier to detect incorrect function calling order
+		this.startTime = null;
+		this.stopTime = null;
+	}
+	//Returns a long with the elapsed time in milliseconds. Used by other functions to get the time before converting it to the correct resolution
+	private getTime(): number{
+		if(this.startTime == null){
+			return 0;
+		}
+		else if(this.stopTime == null){
+			return performance.now() - this.startTime;
+		}
+		else{
+			return this.stopTime - this.startTime;
+		}
+	}
+	//Simultates starting a stopwatch by saving the time
+	public start(): void{
+		//Make sure the stop time is reset
+		this.stopTime = null;
+		//Get the time as close to returning from the function as possible
+		this.startTime = performance.now();
+	}
+	//Simulates stopping a stopwatch by saving the time
+	public stop(): void{
+		//Set the stopTime as close to call time as possible
+		this.stopTime = performance.now();
+		//If the startTime has not been set then reset stopTime
+		if(this.startTime == null){
+			this.stopTime = null;
+		}
+	}
+	//Resets all variables in the stopwatch
+	public reset(): void{
+		//Make sure all variables are reset correctly
+		this.startTime = null;
+		this.stopTime = null;
+	}
+	//Returns the time in nanoseconds
+	public getNano(): number{
+		return this.getTime() * 1000000;
+	}
+	//Returns the time in microseconds
+	public getMicro(): number{
+		return this.getTime() * 1000;
+	}
+	//Returns the time in milliseconds
+	public getMilli(): number{
+		return this.getTime();
+	}
+	//Returns the time in seconds
+	public getSecond(): number{
+		return this.getTime() / 1000;
+	}
+	//Returns the time in minutes
+	public getMinute(): number{
+		return this.getTime() / 60000;
+	}
+	//Returns the time in hours
+	public getHour(): number{
+		return this.getTime() / 3600000;
+	}
+	//Returns the time as a string at the 'best' resolution. (Goal is xxx.xxx)
+	public getStr(): string{
+		//Get the current duraction from time
+		return Stopwatch.getStr(this.getNano());
+	}
+
+	public static getStr(nanoseconds: number): string{
+		let duration: number = nanoseconds;
+		//Reduce the num,ber to the appropriate number of digits. (xxx.x).
+		//This loop works down to seconds
+		let resolution: TIME_RESOLUTION;
+		for(resolution = TIME_RESOLUTION.NANOSECOND;(resolution < TIME_RESOLUTION.SECOND) && (duration >= 1000);++resolution){
+			duration /= 1000;
+		}
+		//Check if the duration needs reduced to minutes
+		if((duration >= 120) && (resolution == TIME_RESOLUTION.SECOND)){
+			//Reduce to minutes
+			duration /= 60;
+			++resolution;
+
+			//Check if the duration needs reduced to hours
+			if(duration >= 60){
+				//Reduce to hours
+				duration /= 60;
+				++resolution;
+			}
+		}
+
+		//Turn the number into a string
+		let time: string = duration.toFixed(3);
+
+		//Tack on the appropriate suffix for resolution
+		switch(resolution){
+			case TIME_RESOLUTION.NANOSECOND: time += " nanoseconds"; break;
+			case TIME_RESOLUTION.MICROSECOND: time += " microseconds"; break;
+			case TIME_RESOLUTION.MILLISECOND: time += " milliseconds"; break;
+			case TIME_RESOLUTION.SECOND: time += " seconds"; break;
+			case TIME_RESOLUTION.MINUTE: time += " minutes"; break;
+			case TIME_RESOLUTION.HOUR: time += " hours"; break;
+			case TIME_RESOLUTION.ERROR:
+			default: throw new InvalidResult("timeResolution was invalid");
+		}
+		//Return the string
+		return time;
+	}
+}