JS 判断手机当前是横屏还是竖屏

orientation官方文档

function rotate() {

      if (window.orientation == 180 || window.orientation == 0) {
      alert('竖屏')
      }
      if (window.orientation == 90 || window.orientation == -90) {
      alert('横屏')
      }
    }
    window.addEventListener("load", rotate, false);
    window.addEventListener("onorientationchange" in window ? "orientationchange" : "resize", rotate, false);