或者你可以用这个…

window.addEventListener("orientationchange", function() {
    if (window.orientation == "90" || window.orientation == "-90") {
        //Do stuff
    }
}, false);

不是270，而是-90(-90)。

大卫·沃尔什的方法更好，更切中要害。

// Listen for orientation changes
window.addEventListener("orientationchange", function() {
  // Announce the new orientation number
  alert(window.orientation);
}, false);

在这些更改期间，窗口。方向属性可能会改变。值为0表示纵向视图，-90表示设备横向向右旋转，90表示设备横向向左旋转。

http://davidwalsh.name/orientation-change

有一种方法可以检测用户是否使用screen.orientation将设备切换到竖屏模式

只需使用下面的代码:

screen.orientation.onchange = function () {
     var type = screen.orientation.type;
     if (type.match(/portrait/)) {
         alert('Please flip to landscape, to use this app!');
     }
}

现在，当用户翻转设备时，onchange将被触发，当用户使用纵向模式时，警报将弹出。

//see also http://stackoverflow.com/questions/641857/javascript-window-resize-event
//see also http://mbccs.blogspot.com/2007/11/fixing-window-resize-event-in-ie.html
/*
Be wary of this:
While you can just hook up to the standard window resize event, you'll find that in IE, the event is fired once for every X and once for every Y axis movement, resulting in a ton of events being fired which might have a performance impact on your site if rendering is an intensive task.
*/

//setup 
window.onresize = function(event) {
    window_resize(event);
}

//timeout wrapper points with doResizeCode as callback
function window_resize(e) { 
     window.clearTimeout(resizeTimeoutId); 
     resizeTimeoutId = window.setTimeout('doResizeCode();', 10); 
}

//wrapper for height/width check
function doResizeCode() {
    if(window.innerHeight > window.innerWidth){
        alert("Please view in landscape");
    }
}

你可以使用CSS3:

@media screen and (orientation:landscape)
{
   body
   {
      background: red;
   }
}