在移动屏幕上删除Skrollr功能

I am trying to remove skrollr functionality on mobile screen sizes.

I have the following code in my footer.php which initiates skrollr.

<script type="text/javascript">
    skrollr.init({
    forceHeight: false
    });
</script>

<script type="text/javascript">
//http://detectmobilebrowsers.com/ + tablets
(function(a) {
     if(/android|avantgo|bada\ ... )
 {
    //Add skrollr mobile on mobile devices.
    document.write('<script type="text/javascript" src="js/skrollr.mobile.min.js"><\/script>');
 }
})(navigator.userAgent||navigator.vendor||window.opera);
</script>

I have asked around and was told to remove the initialization of skrollr in the footer.php and put code in a separate js file (mobile-fix.js)

so I replaced the script code at the bottom of footer.php with

<script type="text/javascript" src="mobile-fix.js"></script>

mobile-fix.js

$(function () {
var skrollrInstance;
var onResize = function () {
    var isMobile = $(window).width() <= 767;
    if (!skrollrInstance && !isMobile) {
        skrollrInstance = skrollr.init({
            forceHeight: false
        });
    } else if(skrollrInstance && isMobile) {
        skrollrInstance.destroy();
        skrollrInstance = null;
    }
};
$(window).on('resize', onResize);
onResize();
});

I have enquened the mobile-fix.js but when removing the code from the footer.php skrollr doesn't work on any screen sizes.

Need to initiate skrollr but remove it on screen sizes > 767