GameStats

GameStats binds to your game loop and provides helpful statistics about your game's performance.

Installation

To install this module through npm, simply use:

$ npm install game-stats

and to use it, you can import it as an ES6 module:

// Webpack
import GameStats from 'game-stats';

// Browser
import GameStats from './node_modules/game-stats/game-stats.js';

Initialization

After installing GameStats, it can be initialized like so:

const gameStats = new GameStats();

GameStats also accepts an options object at initialization with the following options available:

param	type	description	default
historyLimit	number	The amount of items that will be kept in history to be used in calculations. The more history you keep the more accurate the calculations but the longer they will take.	10

So an example of initializating game-stats with options is:

const options = {
  historyLimit: 15
};

const gameStats = new GameStats(options);

Usage

GameStats works with your requestAnimationFrame loop to give you more detailed data about the performance of your game. For example, a typical game loop using requestAnimationFrame would look like this:

const canvas = document.getElementById('myCanvas');
const ctx = canvas.getContext('2d');

let x = canvas.width / 2;
let y = canvas.height - 30;

function drawCircle() {
  ctx.beginPath();
  ctx.arc(x, y - 30, 10, 0, Math.PI * 2);
  ctx.fillStyle = '#0095DD';
  ctx.fill();
  ctx.closePath();
}

function draw(time) {
  ctx.clearRect(0, 0, canvas.width, canvas.height);
  
  drawCircle();

  x += 2;
  y += -2;

  requestAnimationFrame(draw);
}

requestAnimationFrame(draw);

To start gathering data about this game loop, you simply call GameStat's record method after the call to requestAnimationFrame like so:

const canvas = document.getElementById('myCanvas');
const ctx = canvas.getContext('2d');

let x = canvas.width / 2;
let y = canvas.height - 30;

function drawCircle() {
  ctx.beginPath();
  ctx.arc(x, y - 30, 10, 0, Math.PI * 2);
  ctx.fillStyle = '#0095DD';
  ctx.fill();
  ctx.closePath();
}

// Timestamp parameter automatically passed by requestAnimationFrame.
function draw(timestamp) {
  ctx.clearRect(0, 0, canvas.width, canvas.height);
  
  drawCircle();

  x += 2;
  y += -2;

  requestAnimationFrame(draw);

  // Record statistics here, notice the timestamp parameter passed to record.
  gameStats.record(timestamp);
}

// Timestamp is passed to draw automatically without us having to do anything.
requestAnimationFrame(draw);

You'll notice that record takes a parameter, timestamp, which matches the parameter taken by the draw function. If this is new to you, it's a parameter passed by requestAnimationFrame to any function you give it and GameStats uses it to gather information so it must be provided as a parameter to record.

API

After you start recording, the following methods are available:

stats

Gets all of the statistics about the game loop at the current point in time.

The object returned by this method contains the following data:

param	type	description
browser	Object	Information about the browser being used to run the game loop.
browser.name	string	The name of the browser being used.
browser.version	string	The version of the browser being used.
timestamp	DOMHighResTimeStamp	The current timestamp of the game loop.
prevTimestamp	DOMHighResTimeStamp	The previous timestamp of the game loop.
predictedNextTimestamp	number	The predicted next timestamp of the game loop. Note: This is predicted from the average of previous timestamps but is in no way dependable.
delta	number	The time in between the previous and current timestamp.
deltaAverage	number	The average time in between previous and current timestamps. This uses a collection of deltas to compute the average.
frame	number	The current frame that the game is on.
fps	number	The number of frames per second that the game is running at.
fpsAverage	number	The average number of frames per second that the game is running at. This uses a collection of fps values to compute the average.
history	Object	A collection of the histories of certain statistics.
history.timestamps	Array	The history of timestamps.
history.deltas	Array	The history of delta values.

const stats = gameStats.stats();

console.log(stats.fps); // 60, hopefully.

Tests

The tests for game-stats are browser based so to run them you will first need to start the local testing server like so:

$ npm run test

then you will need to navigate to https://localhost/test/index.html in your browser to run all of the available tests for game-stats.

License

MIT