Set the window width to on load and on resize so you can run jQuery at certain browser sizes

jquery-media-queries.js

var        windowWidth;
	
function setWidth() {
	windowWidth = $( window ).width();
}
	
setWidth();
	
$( window ).resize( setWidth );

if ( windowWidth < 768 ) {
	...
}

if ( windowWidth > 320 ) {
	...
}