全屏显示功能（vue）

  <!-- 全屏显示 -->
      <div class="btn-fullscreen" @click="handleFullScreen">
        <i class="el-icon-rank"></i>
      </div>

  // 全屏事件
    handleFullScreen () {
      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;
    }