Arkanoid.js, first steps (Taken from https://github.com/AlphaGit/random-javascript/commit/90e6540100631e1a3ae590c3bde4a21b74f7abd9)

arkanoid.js

window.arkanoid = (function(userOptions) {

  // private fields
  var canvas = null;
  var ctx = null;
  var options = null;

  var defaultOptions = {
    fullWidth: true,
    fullHeight: true,
    stageHeight: 600,
    stageWidth: 1024
  };


  // private methods
  function initOptions(userOptions) {
    options = mergeObjects(defaultOptions, userOptions);
    if (options.fullWidth) options.stageWidth = document.documentElement.clientWidth;
    if (options.fullHeight) options.stageHeight = document.documentElement.clientHeight;
  }

  function mergeObjects(toOverride, overridingWith) {
    for (var property in overridingWith) {
      toOverride[property] = overridingWith[property];
    }
    return toOverride;
  }

  function initCanvas() {
    var body = document.getElementsByTagName("body")[0];
    var height = options.stageWidth;
    var width = options.stageHeight;
    canvas = document.createElement("canvas");
    canvas.width = height;
    canvas.height = width;
    body.appendChild(canvas);
    ctx = canvas.getContext("2d");
  }

  function initAll() {
    initOptions();
    initCanvas();

    var stage = new ArkanoidStage(ctx, options.stageHeight, options.stageWidth);
  }

  // public methods
  return {
    init: initAll
  };
})()