Canvas disappear after click event

I am having a problem where I don't know where to go with it.

http://ift.tt/1HceG73

When i click 1 of the black rectangles it shows "Rectangle 0 clicked" but the canvas disappear.

How can I make it to show it in the canvas ???

for (var i = 0; i < rects.length; i++) {
    if (x > rects[i][0] && x < rects[i][0] + rects[i][2] && y > rects[i][1] && y < rects[i][1] + rects[i][3]) {
        document.getElementById("Display").innerHTML = 'Rectangle ' + i + ' clicked';
    }
}