HTML5如何做横屏适配

<meta name="viewport" content="width=device-width,initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0, user-scalable=yes"/>
<link rel="stylesheet" media="all and (orientation:portrait)" href="portrait.css">
<link rel="stylesheet" media="all and (orientation:landscape)" href="landscape.css">
@media screen and (orientation: portrait) {
  /*竖屏 css*/
} 
@media screen and (orientation: landscape) {
  /*横屏 css*/
}

//JS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！');
            //不用提示
        }
        if (window.orientation === 90 || window.orientation === -90 ){
            //alert('横屏状态！');
            //不用提示
        } 
    }, false);

移动端的浏览器一般都支持window.orientation这个参数，通过此参数可判断手机是处在横屏还是竖屏状态