多屏判断css改写

function replaceBodyClass(){
    for(var i in map){
       if(map[i](width)){
          document.body.className = document.body.className.replace(/screen-\w+/, "screen-"+i)
          break
       }
    }
}

map["1280"] = function(width){
   return width <= 1300
}


map["x1"] = function(width){
   return width > = 1580
}

map["1"] = function(width){
   return  width > = 1400 && width < 1580
}