Prevent background image from resize on scrolling

Question

I have background image that is resizing a little bit when I scroll from the top on mobile devices. And it returns to its size when I scroll to the top agai

Answer 1

If the background-image is resizing on initial scroll, I assume the element with that background must have a dynamic height, generated using either vw/vh in the CSS or JS/jQ script. I ran into this same problem, and I found what I believe to be the correct method in resolving this issue (at least until mobile browsers provide their own workaround).

Using a simple jQuery function, you can store the window's width on page load, and use that to restrict the container's resizing function to viewport sizes wider than the desktop breakpoint (992px+) and narrower viewports so long as the viewport width changes, not just the height. This way, on mobile and tablet devices, when you scroll, there is only a vertical viewport resize, so the resize function is not triggered.

var breakpoint = 991;
var bgHeight = function() {
    $('#bg').css('height', $(window).height() + 'px');
}; bgHeight();
var windowWidth = $(window).height();
$(window).on('resize', function() {
    if ((($(this).width() <= breakpoint) && ($(this).width() != windowWidth))
        || ($(this).width() > breakpoint)) {
        bgHeight();
    }
    windowWidth = $(window).width();
});

CodePen: https://codepen.io/brandonmcconnell/pen/jayYbB