var apronURL = "imgs/apron1.jpg";

if (document.images) {
     var apron1 = new Image();
     apron1.src = "imgs/apron1.jpg";

     var apron2 = new Image();
     apron2.src = "imgs/apron2.jpg";
	 
	 var apron3 = new Image();
	 apron3.src = "imgs/apron3.jpg";
	 
	 var catalog = new Image();
	 catalog.src = "imgs/catalog.jpg";
}

function changeApron() {
     if (document.images) {
        if (apronURL == "imgs/apron1.jpg") apronURL = "imgs/apron2.jpg";
		else if (apronURL == "imgs/apron2.jpg") apronURL = "imgs/apron3.jpg";
		else if (apronURL == "imgs/apron3.jpg") apronURL = "imgs/catalog.jpg";
		else if (apronURL == "imgs/catalog.jpg") apronURL = "imgs/apron1.jpg";
		
         document.myApron.src = apronURL;
	}
}

function changeApronBack() {
     if (document.images) {
        if (apronURL == "imgs/apron1.jpg") apronURL = "imgs/catalog.jpg";
		else if (apronURL == "imgs/apron2.jpg") apronURL = "imgs/apron1.jpg";
		else if (apronURL == "imgs/apron3.jpg") apronURL = "imgs/apron2.jpg";
		else if (apronURL == "imgs/catalog.jpg") apronURL = "imgs/apron3.jpg";
		
         document.myApron.src = apronURL;
	}
}