Stack Overflow has a good post on determining if two rectangles are overlapping.  I used the discussed algorithm to check for an overlap and then move one away.  I’m only moving up or down depending on which rectangle is higher or lower and if it will fit in a specified areas min or max.

<script type="text/javascript">

var rectA = {x: 2, y: 5, width: 6, height: 6};
var rectB = {x: 4, y: 10, width: 6, height: 6};
var area = {min: 0, max: 100};

var overlap = rectOverlap(rectA,rectB);
alert("Does rectA and rectB overlap? " + overlap);

if(overlap)
{
if(rectA.y >= rectB.y)
{
if(increaseY(rectA.width, rectB.y + rectB.height, area.max))
{
rectA.y = rectB.y + rectB.height + 1;
}
else if (rectA.y - rectB.height > area.min)
{
rectB.y = rectA.y - rectB.height;
}
}
else
{
if(increaseY(rectB.width, rectA.y + rectA.height, area.max))
{
rectB.y = rectA.y + rectA.height + 1;
}
else if (rectB.y - rectA.height > area.min)
{
rectA.y = rectB.y - rectA.height;
}
}
}

alert("Does rectA and rectB overlap? " + rectOverlap(rectA,rectB));

function increaseY(width, bottomEdge, Max)
{
return (bottomEdge + width < Max);
}

function valueInRange(value, min, max)
{

return (value <= max) && (value >= min);

}

function rectOverlap(A, B)
{
var xOverlap = valueInRange(A.x, B.x, B.x + B.width) ||
valueInRange(B.x, A.x, A.x + A.width);

var yOverlap = valueInRange(A.y, B.y, B.y + B.height) ||
valueInRange(B.y, A.y, A.y + A.height);

return xOverlap && yOverlap;
}

</script>