Gamedev.tutsplus Introduction to Spritesheet Animation - single cycle

A demo of creating a spritesheet animation

by Steven Lambert

HTML

<canvas id="canvas" width="150" height="150"></canvas>

CSS

canvas {
    border: 1px solid black;
}

JavaScript

/**
 * Copyright (C) 2013 Steven Lambert
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this
 * software and associated documentation files (the "Software"), to deal in the Software
 * without restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to the following
 * conditions:
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
 * OR OTHER DEALINGS IN THE SOFTWARE.
 */

/**
 * Full tutorial can be found on gamedev.tutsplus.com
 */

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

/**
 * Creates a Spritesheet animation.
 * @param {string}  - Path to the image.
 * @param {number}  - Width (in px) of each frame.
 * @param {number}  - Height (in px) of each frame.
 * @param {number}  - Number of frames to wait for before transitioning the animation.
 * @param {number}  - Last frame number of the animation.
 */
function SpriteSheet(path, frameWidth, frameHeight, frameSpeed, endFrame) {

  var image = new Image();
  var framesPerRow;

  // calculate the number of frames in a row after the image loads
  var self = this;
  image.onload = function() {
    framesPerRow = Math.floor(image.width / frameWidth);
  };

  image.src = path;

  var currentFrame = 0;        // the current frame to draw
  var counter = 0;             // keep track of frame rate

  // Update the animation
  this.update = function() {

    // update to the next frame if it is time
    if...