An excerpt of how the original SkiFree port that I created looked, in essence.

skifree-v1.js

var skier;
var trees = [];
var mouseX = getCentreOfViewport();
var mouseY = mainCanvas.height;

dContext.getLoadedImage = function (imgPath) {
	if (images[imgPath]) {
		return images[imgPath];
	}
};

skier = new Skier(sprites.skier);
tree = new Sprite(sprites.smallTree);

skier.setPosition(mouseX, getMiddleOfViewport());
setInterval(function () {
  // Draw the bastards
});