判断手机是横屏还是竖屏幕

@media screen and (orientation: portrait) {
  /*竖屏 css*/
} 
@media screen and (orientation: landscape) {
  /*横屏 css*/
}
分开写在2个CSS中
竖屏




<link rel="stylesheet" media="all and (orientation:portrait)" href="portrait.css">
横屏




<link rel="stylesheet" media="all and (orientation:landscape)" href="landscape.css">


//判断手机横竖屏状态：
window.addEventListener("onorientationchange" in window ? "orientationchange" : "resize", function() {
        if (window.orientation === 180 || window.orientation === 0) {
            alert('竖屏状态！');
        }
        if (window.orientation === 90 || window.orientation === -90 ){
            alert('横屏状态！');
        } 
    }, false);
//移动端的浏览器一般都支持window.orientation这个参数，通过这个参数可以判断出手机是处在横屏还是竖屏状态。