我想要更改下面的javascript,以便如果屏幕分辨率为768px或更低,header_height变量会减少到50而不是100,否则它会保持在100.谢谢提前一切协助!如何在javascript中执行css媒体查询等效
<script>
$(window).scroll(function() {
\t var elem = $('.header');
\t var header_height \t = 100;
\t \t var header_top \t \t = elem.offset().top;
\t \t var current_top \t \t = $(this).scrollTop();
\t if (current_top > header_height && !elem.hasClass('fixed'))
\t \t {
\t \t elem.addClass('fixed');
\t \t \t $('body').addClass('fixed-padding');
\t }
\t else if(current_top <= header_height && elem.hasClass('fixed'))
\t \t {
\t \t elem.removeClass('fixed');
\t \t \t $('body').removeClass('fixed-padding');
\t \t }
\t });
</script>