PouchDB emit object from an array of objects

问题

I would like to search trough an array of objects (that are encapsulated in one big object), and emit only the one of the internal objects. So let's suppose I have a JSON inserted into PouchDB that is looks like this:

{
"_id": "5eaa6d20-2019-44e9-8aba-88cfaf8e02542",
"data": [
    {
        "id": 1452,
        "language": "java"
    },
    {
        "id": 18787453,
        "language": "javascript"
    },
    {
        "id": 145389721,
        "language": "perl"
    }
  ]
}

How to get PouchDB to return the following result when searching for a language with an id = 145389721:

{
  "id": 145389721,
  "language": "perl"
}

Thanks!

回答1:

In the scenario above the easiest way, using typescript, is to write a temp query:

        db.query((doc, emit) => {
          for (let element of doc.data) {
            if (element.id === 145389721) {
              emit(element);
            }
          }
        }).then((result) => {
          for (let row of result.rows) {
            console.log(row.key);
          }
        })

Using permanent queries it would have looked like this:

let index = {
  _id: '_design/my_index',
  views: {
    "by_id": {
      "map": "function(doc) {for (let element of doc.data) {emit(element.id, element); }}"
    }
  }
};

// save it
this.db.put(index).catch(error => {
  console.log('Error while inserting index', error);
});

//query it 
this.db.query('my_index/by_id', { startkey: 145389721, endkey: 145389721}).then(result => {
  for (let row of result.rows) {
    console.log(row.value);
  }
}).catch(error => {
  console.log('Error while querying the database with an index', error);
});

来源：https://stackoverflow.com/questions/42636085/pouchdb-emit-object-from-an-array-of-objects