关于 rem在移动端横屏竖屏的适配问题

function setRem(){
    var is_horizontal = 1, remNum = 13.34, c_width;
    if(request('is_horizontal')){
        is_horizontal = request('is_horizontal');
    }
    if(is_horizontal == 0){
        remNum = 7.5;
    }
    c_width = document.documentElement.clientWidth;
    document.querySelector('html').style.fontSize = (c_width/remNum > 80 ? 80 + 'px' : c_width/remNum + 'px');
};