Question

For example the below image is at initial window position..

When I will decrease the window size then the number of divs should change accordingly.

Edit : Each map represents a Div.

Answer 1

Get sizes of maps:

var maps = document.getElementsByClassName('.map');
for(var i = 0; i < maps.length; i++){
    var map = maps[i];
    var rect = map.getClientRects()[0];
    map.left = rect.left;
    map.top = rect.top;
    map.width = rect.width;
    map.height = rect.height;
}

On screen resize event, where you will check:

for(var i = 0; i < maps.length; i++){
    if(maps[i].left + maps[i].width > screen.width ||
       maps[i].top + maps[i].height> screen.height)
        maps[i].style.display = 'none';
    else
        maps[i].style.display = 'block';
}

I have not tested, hope it works