$(function(){
//背景自适应
bg_size();
$(window).on('resize',function(){
bg_size();
});
});
//背景自适应
function bg_size(){
var bg_h = 860;
var bg_w = 1920;
var win_h = $(window).height();
var win_w = $(window).width();
if(bg_h/bg_w >= win_h/win_w){
$('.s-bg').attr('style',"width:100%;position:absolute;left:0;top:50%;margin-top:-"+bg_h*(win_w/bg_w)/2+"px");
}else{
$('.s-bg').attr('style',"height:100%;position:absolute;top:0;left:50%;margin-left:-"+bg_w*(win_h/bg_h)/2+"px");
}
}