[Stopwatch.mjs] C#'s System.Diagnostics.Stopwatch (roughly) implemented in C#.

Stopwatch.mjs

"use strict";

/**
 * Stopwatch class for timing things.
 * Based on System.Diagnostics.Stopwatch from .NET: https://docs.microsoft.com/en-us/dotnet/api/system.diagnostics.stopwatch
 */
class Stopwatch {
	/**
	 * Creates a new (stopped) stopwatch.
	 */
	constructor() {
		this.start = null;
		this.end = null;
		
		this.is_high_resolution = false;
	}
	
	/**
	 * The number of seconds that have elapsed since the stopwatch was started.
	 * @return {number}
	 */
	get elapsed_seconds() {
		return (this.end == null ? new Date() : this.end) - this.start;
	}
	
	/**
	 * The number of milliseconds that have elapsed since the stopwatch was started.
	 * @return {number}
	 */
	get elapsed_milliseconds() {
		return this.elapsed_seconds / 1000;
	}
	
	/**
	 * Whether the stopwatch is currently running or not.
	 * @return {number}
	 */
	get is_running() {
		return this.start !== null && this.end !== null;
	}
	
	/**
	 * Starts the stopwatch.
	 */
	start() {
		this.start = new Date();
		this.end = null;
	}
	
	/**
	 * Resets the stopwatch, stopping it and wiping the internal state in the 
	 * process.
	 */
	reset() {
		this.start = null;
		this.end = null;
	}
	
	/**
	 * Restarts the stopwatch, keeping it running.
	 */
	restart() {
		this.start();
	}
	
	/**
	 * Stops the stopwatch.
	 */
	stop() {
		this.end = new Date();
	}
	
	/**
	 * Stops the stopwatch and returns the number of elapsed seconds.
	 * @return {number} The number of seconds elapsed since the stopwatch was started, as a float.
	 */
	end() {
		this.stop();
		return this.elapsed_seconds;
	}
	
	/**
	 * Returns a string that represents this stopwatch instance.
	 * @return {string}
	 */
	toString() {
		return `[StopWatch, start=${start || "null"}, end=${end || "null"} | elapsed_seconds=${this.elapsed_seconds}]`;
	}
}

/**
 * Creates a new stopwatch, starts it, and returns the result.
 * @return {Stopwatch} A new started stopwatch.
 */
function start_new() {
	let result = new Stopwatch();
	result.start();
	return result;
}

Stopwatch.StartNew = start_new;

export { start_new };
export default Stopwatch;