全屏

        fullScreen () {
          if (this.isfullScreen) {
            var docElm = document.documentElement
            if (docElm.requestFullscreen) {
              docElm.requestFullscreen()
            } else if (docElm.mozRequestFullScreen) {
              docElm.mozRequestFullScreen()
            } else if (docElm.webkitRequestFullScreen) {
              docElm.webkitRequestFullScreen()
            } else if (elem.msRequestFullscreen) {
              elem.msRequestFullscreen()
            }
            this.isfullScreen = false
          } else {
            if (document.exitFullscreen) {
              document.exitFullscreen()
            } else if (document.mozCancelFullScreen) {
              document.mozCancelFullScreen()
            } else if (document.webkitCancelFullScreen) {
              document.webkitCancelFullScreen()
            } else if (document.msExitFullscreen) {
              document.msExitFullscreen()
            }
            this.isfullScreen = true
          }
        },