db.collection(变量名)

data{
  DBID: 'dbname'
}
getdb(){
  db.collection(this.data.DBID).get()
    .then(res =>{
       console.log(res.data)
    })  
}

data{
  DBID: 'dbname'
}

getdb(){
    let dbname = this.data.DBID

    db.collection(dbname).get()
        .then(res =>{
           console.log(res.data)
        })
}