jQuery do różnych wielkości okna

var $window = $(window);
 
function checkWidth() {
    var windowsize = $window.width();
    if (windowsize < 900) {
 
    }
    else if (windowsize > 899) {           
 
    }
}
// Execute on load
checkWidth();
// Bind event listener
$(window).resize(checkWidth);

$(window).height();   // returns height of browser viewport
$(document).height(); // returns height of HTML document
$(window).width();   // returns width of browser viewport
$(document).width(); // returns width of HTML document
 

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