网页全屏及退出全屏

一、实现页面全屏

    function doFullscreen (el) {
      if (el == null) {
        el = document.documentElement
      }
      const func = el.requestFullscreen || el.requestFullScreen || el.webkitRequestFullScreen || el.mozRequestFullScreen || el.msRequestFullScreen
      if (!func) {
        throw new Error("您的浏览器不支持全屏模式");
      }
      func.call(el)
    }

二、退出全屏

    function doExitFullscreen () {
      const func = document.exitFullscreen || document.exitFullScreen || document.webkitCancelFullScreen || document.mozCancelFullScreen || document.msExitFullscreen
      func && func.call(document);
    }

三、检测是否为全屏

    function doCheckFullscreen () {
      return !!(document.fullscreenElement || document.webkitFullscreenElement || document.mozFullScreenElement || document.msFullscreenElement)
    }