有效解决问题 : Failed to execute ‘exitFullscreen‘ on ‘Document‘: Document not active 

在未全屏的情况下触发exitFullscreen，会报这个错。

<el-button class="screen" @click="toggleFullscreen">全屏</el-button>

fullscreen: false

// 全屏、退出全屏切换
    toggleFullscreen() {
      let element = document.documentElement;
      if (this.fullscreen) {
        if (document.exitFullscreen) {
          document.exitFullscreen();
        } else if (document.webkitCancelFullScreen) {
          document.webkitCancelFullScreen();
        } else if (document.mozCancelFullScreen) {
          document.mozCancelFullScreen();
        } else if (document.msExitFullscreen) {
          document.msExitFullscreen();
        }
      } else {
        if (element.requestFullscreen) {
          element.requestFullscreen();
        } else if (element.webkitRequestFullScreen) {
          element.webkitRequestFullScreen();
        } else if (element.mozRequestFullScreen) {
          element.mozRequestFullScreen();
        } else if (element.msRequestFullscreen) {
          // IE11
          element.msRequestFullscreen();
        }
      }
      this.fullscreen = !this.fullscreen;
    }

mounted() {
    // 退出全屏后要执行的动作
    window.onresize = ()=>{
        let isFull = document.mozFullScreen||
        document.fullScreen ||
        //谷歌浏览器及Webkit内核浏览器
        document.webkitIsFullScreen ||
        document.webkitRequestFullScreen ||
        document.mozRequestFullScreen ||
        document.msFullscreenEnabled
        if(isFull === undefined) {
          this.fullscreen = false;
        }
      
    }

  }