1.在mounted中加入如下代码

     window.addEventListener('beforeunload', e => this.beforeunloadHandler(e))
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2. 在methods中加入如下代码

 beforeunloadHandler (e) {
      e = e || window.event
      if (e) {
        e.returnValue = '关闭提示'
      }
      return '关闭提示'
    }
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3. 最后销毁

destroyed () {
   window.removeEventListener('beforeunload', e => this.beforeunloadHandler(e))
 },
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