var aryImages = new Array();

aryImages['nyc1_A'] = "images/nyc1_A.jpg";
aryImages['nyc1_B'] = "images/nyc1_B.jpg";

aryImages['nyc2_A'] = "images/nyc2_A.jpg";
aryImages['nyc2_B'] = "images/nyc2_B.jpg";
aryImages['nyc2_C'] = "images/nyc2_C.jpg";
aryImages['nyc2_D'] = "images/nyc2_D.jpg";

aryImages['conc1_A'] = "images/conc1_A.jpg";
aryImages['conc1_B'] = "images/conc1_B.jpg";
aryImages['conc1_C'] = "images/conc1_C.jpg";
aryImages['conc1_D'] = "images/conc1_D.jpg";

aryImages['conc2_A'] = "images/conc2_A.jpg";
aryImages['conc2_B'] = "images/conc2_B.jpg";
aryImages['conc2_C'] = "images/conc2_C.jpg";
aryImages['conc2_D'] = "images/conc2_D.jpg";
aryImages['conc2_E'] = "images/conc2_E.jpg";
aryImages['conc2_F'] = "images/conc2_F.jpg";
aryImages['conc2_G'] = "images/conc2_G.jpg";
aryImages['conc2_H'] = "images/conc2_H.jpg";
aryImages['conc2_I'] = "images/conc2_I.jpg";
aryImages['conc2_J'] = "images/conc2_J.jpg";

for (i=0; i < aryImages.length; i++) {
	var preload = new Image();
	preload.src = aryImages[i];
}

function swap(imgIndex, imgTarget) {
	document[imgTarget].src = aryImages[imgIndex];
}