jQuery：设置if else语句根据浏览器宽度执行偏移量

Finishing up a parallax, one page site and I've got a fixed nav, so I have to offset the various div's / sections on my page so they don't get cut off on top. Problem is performing this for different browser widths, since my fixed nav will be about half the height on mobile as it is on desktop.Finishing up a parallax, one page site and I've