检测两个矩形dom是否重叠或求重叠的大小

gistfile1.txt

function isRegionOverlap(region1, region2) {
    var min = Math.min;
    var max = Math.max;
    var left   = max(region1.left,region2.left);
    var top    = min(-region1.top,-region2.top);
    var right  = min(region1.right,region2.right);
    var bottom = max(-region1.bottom,-region2.bottom);
    return right > left && top >  bottom;
}

function isOverlap(dom1,dom2){
	var region1 = dom1.getBoundingClientRect();
	var region2 = dom2.getBoundingClientRect();
	return overlapRegion(region1,region2);
}