监听el-dialog宽度适配

 修改el-dialog 试了好多方法不生效，原来修改dialog必须在非scoped环境下

console.log(document.body.clientWidth)
      var val = document.body.clientWidth
      const def = 800 // 默认宽度
      if (val < def) {
        this.dialogWidth = '80%'
      } else {
        // this.dialogWidth = '30%'
        this.dialogWidth = 400 + 'px'       
      }

data()
    {
    return{
        dialogWidth:'',
    }
    }
<el-dialog title="个人信息验证" :visible.sync="dialogFormVisible" :width="dialogWidth" >
</el-dialog>