function addLoadEvent(func) 
{
	var oldonload = window.onload;
  	if (typeof window.onload != 'function') 
  	{
		window.onload = func;
  	} 
 	 else 
  	{
		window.onload = function() 
		{
	  		if (oldonload) 
	  		{
				oldonload();
			}
	  	func();
		}
  	}
}

addLoadEvent(showMap);