How do I apply jquery for mobile only?

To write jQuery that only applies for mobile devices, just use the sample below and it worked for me.

if(window.outerWidth < 425) {
  alert('your jquery code here - it fires for mobile device only');
}

Edit: Was the wrong symbol less than

It's always very hard to detect whether its a mobile device's browser or a laptop with a touch screen. So instead of detecting that; if you are concern about the screen size then i will recommend you to detect the screen size and if its below certain level(lets say below 481px) then we will assume that its a mobile screen and will execute your needed code as follows:

$(document).ready(function () {
    $(window).on("resize", function (e) {
        checkScreenSize();
    });

    checkScreenSize();
    
    function checkScreenSize(){
        var newWindowWidth = $(window).width();
        if (newWindowWidth < 481) {
            $('.right').insertBefore('.left');
        }
        else
        {
            $('.left').insertBefore('.right');
        }
    }
});