Question

我打印时

让app = express（）

在控制台上它像这样打印。

{ [EventEmitter: app]
  _events: { mount: [Function: onmount] },
  _eventsCount: 1,
  _maxListeners: undefined,
  setMaxListeners: [Function: setMaxListeners],
  getMaxListeners: [Function: getMaxListeners],
  emit: [Function: emit],
  addListener: [Function: addListener],
  on: [Function: addListener],
  prependListener: [Function: prependListener],
  once: [Function: once], 
  ...
}

在代码片段中，有一个on：函数等...因此，我认为这使我可以像在此app上一样使用function.on（...）

const Grid = require('gridfs-stream');

let gfs;
       conn.once('open', () => {
    // Init stream
    gfs = Grid(conn.db, mongoose.mongo);
    gfs.collection('uploads');
    console.log(gfs);
 });

但是，当我在控制台上打印gfs对象时，它会打印出来。这是我的示例链接：https://github.com/qkreltms/mongodb_simple_file_upload_to_db_example/blob/master/app.js

Grid {
  db:
   Db {
     _events:
      { reconnect: [Function], close: [Function], timeout: [Function] },
     _eventsCount: 3,
     _maxListeners: undefined,
     s:
      { databaseName: 'imgSaveTest',
        dbCache: {},
        children: [],
        topology: [Server],
        options: [Object],
        logger: [Logger],
        bson: BSON {},
        readPreference: [ReadPreference],
        bufferMaxEntries: -1,
        parentDb: null,
        pkFactory: undefined,
        nativeParser: undefined,
        promiseLibrary: [Function: Promise],
        noListener: false,
        readConcern: undefined },
     serverConfig: [Getter],
     bufferMaxEntries: [Getter],
     databaseName: [Getter] },
  mongo:
   { [Function]
     MongoError: [Function: MongoError],
     MongoNetworkError: [Function: MongoNetworkError],
     Admin: [Function: Admin],
     MongoClient:
      { [Function: MongoClient] super_: [Function], connect: [Circular] },
     Db:
      { [Function: Db]
        super_: [Function],
        SYSTEM_NAMESPACE_COLLECTION: 'system.namespaces',
        SYSTEM_INDEX_COLLECTION: 'system.indexes',
        SYSTEM_PROFILE_COLLECTION: 'system.profile',
        SYSTEM_USER_COLLECTION: 'system.users',
        SYSTEM_COMMAND_COLLECTION: '$cmd',
        SYSTEM_JS_COLLECTION: 'system.js' },
     Collection: [Function: Collection],
     Server: [Function: Server],
     ReplSet: [Function: ReplSet],
     Mongos: [Function: Mongos],
     ReadPreference:
      { [Function: ReadPreference]
        PRIMARY: 'primary',
        PRIMARY_PREFERRED: 'primaryPreferred',
        SECONDARY: 'secondary',
        SECONDARY_PREFERRED: 'secondaryPreferred',
        NEAREST: 'nearest',
        isValid: [Function],
        primary: [ReadPreference],
        primaryPreferred: [ReadPreference],
        secondary: [ReadPreference],
        secondaryPreferred: [ReadPreference],
        nearest: [ReadPreference] },
     GridStore:
      { [Function: GridStore]
        DEFAULT_ROOT_COLLECTION: 'fs',
        DEFAULT_CONTENT_TYPE: 'binary/octet-stream',
        IO_SEEK_SET: 0,
        IO_SEEK_CUR: 1,
        IO_SEEK_END: 2,
        exist: [Function],
        list: [Function],
        read: [Function],
        readlines: [Function],
        unlink: [Function] },
     Chunk: { [Function: Chunk] DEFAULT_CHUNK_SIZE: 261120 },
     Logger:
      { [Function: Logger]
        reset: [Function],
        currentLogger: [Function],
        setCurrentLogger: [Function],
        filter: [Function],
        setLevel: [Function] },
     AggregationCursor:
      { [Function: AggregationCursor] super_: [Function], INIT: 0, OPEN: 1, CLOSED: 2 },
     CommandCursor:
      { [Function: CommandCursor] super_: [Function], INIT: 0, OPEN: 1, CLOSED: 2 },
     Cursor:
      { [Function: Cursor] super_: [Function], INIT: 0, OPEN: 1, CLOSED: 2, GET_MORE: 3 },
     GridFSBucket: { [Function: GridFSBucket] super_: [Function] },
     CoreServer:
      { [Function: Server]
        super_: [Function],
        enableServerAccounting: [Function],
        disableServerAccounting: [Function],
        servers: [Function] },
     CoreConnection:
      { [Function: Connection]
        super_: [Function],
        enableConnectionAccounting: [Function],
        disableConnectionAccounting: [Function],
        connections: [Function] },
     Binary:
      { [Function: Binary]
        BUFFER_SIZE: 256,
        SUBTYPE_DEFAULT: 0,
        SUBTYPE_FUNCTION: 1,
        SUBTYPE_BYTE_ARRAY: 2,
        SUBTYPE_UUID_OLD: 3,
        SUBTYPE_UUID: 4,
        SUBTYPE_MD5: 5,
        SUBTYPE_USER_DEFINED: 128,
        Binary: [Circular] },
     Code: { [Function: Code] Code: [Circular] },
     Map: { [Function: Map] Map: [Circular] },
     DBRef: { [Function: DBRef] DBRef: [Circular] },
     Double: { [Function: Double] Double: [Circular] },
     Int32: { [Function: Int32] Int32: [Circular] },
     Long:
      { [Function: Long]
        fromInt: [Function],
        fromNumber: [Function],
        fromBits: [Function],
        fromString: [Function],
        INT_CACHE_: [Object],
        TWO_PWR_16_DBL_: 65536,
        TWO_PWR_24_DBL_: 16777216,
        TWO_PWR_32_DBL_: 4294967296,
        TWO_PWR_31_DBL_: 2147483648,
        TWO_PWR_48_DBL_: 281474976710656,
        TWO_PWR_64_DBL_: 18446744073709552000,
        TWO_PWR_63_DBL_: 9223372036854776000,
        ZERO: [Long],
        ONE: [Long],
        NEG_ONE: [Long],
        MAX_VALUE: [Long],
        MIN_VALUE: [Long],
        TWO_PWR_24_: [Long],
        Long: [Circular] },
     MinKey: { [Function: MinKey] MinKey: [Circular] },
     MaxKey: { [Function: MaxKey] MaxKey: [Circular] },
     ObjectID:
      { [Function: ObjectID]
        index: 4899462,
        createPk: [Function: createPk],
        createFromTime: [Function: createFromTime],
        createFromHexString: [Function: createFromHexString],
        isValid: [Function: isValid],
        ObjectID: [Circular],
        ObjectId: [Circular] },
     ObjectId:
      { [Function: ObjectID]
        index: 4899462,
        createPk: [Function: createPk],
        createFromTime: [Function: createFromTime],
        createFromHexString: [Function: createFromHexString],
        isValid: [Function: isValid],
        ObjectID: [Circular],
        ObjectId: [Circular] },
     Symbol: { [Function: Symbol] Symbol: [Circular] },
     Timestamp:
      { [Function: Timestamp]
        fromInt: [Function],
        fromNumber: [Function],
        fromBits: [Function],
        fromString: [Function],
        INT_CACHE_: [Object],
        TWO_PWR_16_DBL_: 65536,
        TWO_PWR_24_DBL_: 16777216,
        TWO_PWR_32_DBL_: 4294967296,
        TWO_PWR_31_DBL_: 2147483648,
        TWO_PWR_48_DBL_: 281474976710656,
        TWO_PWR_64_DBL_: 18446744073709552000,
        TWO_PWR_63_DBL_: 9223372036854776000,
        ZERO: [Timestamp],
        ONE: [Timestamp],
        NEG_ONE: [Timestamp],
        MAX_VALUE: [Timestamp],
        MIN_VALUE: [Timestamp],
        TWO_PWR_24_: [Timestamp],
        Timestamp: [Circular] },
     BSONRegExp: { [Function: BSONRegExp] BSONRegExp: [Circular] },
     Decimal128:
      { [Function: Decimal128] fromString: [Function], Decimal128: [Circular] },
     connect: [Circular],
     instrument: [Function] },
  curCol: 'uploads',
  _col:
   Collection {
     s:
      { pkFactory: [Function],
        db: [Db],
        topology: [Server],
        dbName: 'imgSaveTest',
        options: [Object],
        namespace: 'imgSaveTest.uploads.files',
        readPreference: [ReadPreference],
        slaveOk: true,
        serializeFunctions: undefined,
        raw: undefined,
        promoteLongs: undefined,
        promoteValues: undefined,
        promoteBuffers: undefined,
        internalHint: null,
        collectionHint: null,
        name: 'uploads.files',
        promiseLibrary: [Function: Promise],
        readConcern: undefined,
        writeConcern: undefined } } }

gfs.collection（'uploads'）;

您可以看到其中没有收集功能，但是即使控制台上不存在它也可以使用。所以问题是收集功能从何而来？

谢谢。

Answer 1

在这种情况下

let app = express()

记录

express函数，并在控制台中显示其功能。

但是在这种情况下

const Grid = require('gridfs-stream');

Grid尚未被调用，您在调用它后正在检查功能。调用GFS后尝试控制台gfs

gfs = Grid(conn.db, mongoose.mongo);
console.log(gfs)

Answer 2

好吧，我现在甚至都不知道为什么控制台上没有收集功能，但这是我想要的答案。

链接：https://github.com/qkreltms/mongodb_simple_file_upload_to_db_example/blob/master/app.js

Grid.prototype.collection = function (name) {
  this.curCol = name || this.curCol || this.mongo.GridStore.DEFAULT_ROOT_COLLECTION;
  return this._col = this.db.collection(this.curCol + ".files");
}

使用功能不存在可能吗？

2 个答案: