TileMap rotation

TileMap.js

function Tile(type) {
  this.type = type;
}

function TileMap(w, h, initial) {
  this._width = w;
  this._height = h;
  this.rotation = 0;
  this.reset(initial);
}

TileMap.prototype.reset = function(initial) {
  this.map = [];
  for(var y = 0; y < this._height; ++y) {
    this.map[y] = [];
    for(var x = 0; x < this._width; ++x) {
      this.map[y][x] = new Tile(initial || 0);
    }
  }
}

TileMap.prototype.getWidth = function() {
  return (this.rotation % 2 != 0) ? this._height : this._width;
}

TileMap.prototype.getHeight = function() {
  return (this.rotation % 2 != 0) ? this._width : this._height;
}

TileMap.prototype.get = function(x, y) {
  var realX = x, realY = y;
  if(this.rotation % 2 != 0) {
    realX ^= realY;
    realY ^= realX;
    realX ^= realY;
  }
  if(this.rotation == 1) {
    realX = this._width - realX - 1;
  } else if(this.rotation == 3) {
    realY = this._height - realY - 1;
  } else if(this.rotation == 2) {
    realX = this._width - realX - 1;
    realY = this._height - realY - 1;
  }
  if(realX >= 0 && realX < this._width &&
    realY >= 0 && realY < this._height) { 
    return this.map[realY][realX];
  } else {
    return null;
  }
}

TileMap.prototype.set = function(x, y, value) {
  var realX = x, realY = y;
  if(this.rotation % 2 != 0) {
    realX ^= realY;
    realY ^= realX;
    realX ^= realY;
  }
  if(this.rotation == 1) {
    realX = this._width - realX - 1;
  } else if(this.rotation == 3) {
    realY = this._height - realY - 1;
  } else if(this.rotation == 2) {
    realX = this._width - realX - 1;
    realY = this._height - realY - 1;
  }
  if(realX >= 0 && realX < this._width &&
    realY >= 0 && realY < this._height) { 
    this.map[realY][realX] = value;
  }
}

TileMap.prototype.rotate90 = function() {
  this.rotation += 1;
  this.rotation %= 4;
}

TileMap.prototype.rotate180 = function() {
  this.rotation += 2;
  this.rotation %= 4;
}

TileMap.prototype.rotate270 = function() {
  this.rotation += 3;
  this.rotation %= 4;
}

TileMap.fromArray = function(arr) {
  var tileMap = new TileMap(arr[0].length, arr.length);
  var w = tileMap.getWidth();
  var h = tileMap.getHeight();
  for(var y = 0; y < h; ++y) {
    for(var x = 0; x < w; ++x) {
      var tile = tileMap.get(x, y);
      tile.type = arr[y][x];
    }
  }
  return tileMap;
}