var num = 4;

function swap(what){
	for(var i = 0; i < num; i++)
	{
		document.getElementById('swap'+i).style.display = 'none';
		document.getElementById('default'+i).style.display = 'block';
	}
		document.getElementById('swap'+what).style.display = 'block';
		document.getElementById('default'+what).style.display = 'none';
}
var createStyle = document.createElement('style');
var createStyleProp = document.createTextNode('.hidden { display:none; }');
createStyle.appendChild(createStyleProp);
document.getElementsByTagName('head')[0].appendChild(createStyle);