Question

所以我有这个脚本：

var db = require('mongoskin').db('localhost:27017/titles', {safe:true});
var titles = db.collection('titles');

title = titles.findOne(function(err, result){
if (err) throw err;
return result.title;
});

console.log(title)

集合中的这个BSON对象：

{"title": "Hello World", "postNumber": 0, "_id": ObjectId("509eeffbf8f11e8813000001")}

我的目标是获取字符串“Hello World”输出到控制台，但我得到了这个：

{ emitter: { _events: { open: [Object] }, _maxListeners: 50 },
  state: 1,
  options: undefined,
  skinDb:
   { emitter: { _events: [Object], _maxListeners: 100 },
     state: 1,
     _dbconn:
      { databaseName: 'titles',
    serverConfig: [Object],
    options: [Object],
    _applicationClosed: false,
    native_parser: true,
    bsonLib: [Object],
    bson: {},
    bson_deserializer: [Object],
    bson_serializer: [Object],
    _state: 'connecting',
    pkFactory: [Object],
    forceServerObjectId: false,
    safe: true,
    notReplied: {},
    isInitializing: true,
    auths: [],
    openCalled: true,
    commands: [],
    _callBackStore: [Object],
    logger: [Object],
    slaveOk: false,
    tag: 1352682584657,
    eventHandlers: [Object],
    serializeFunctions: false,
    raw: false,
    recordQueryStats: false,
    reaperEnabled: false,
    _lastReaperTimestamp: 1352682584657,
    retryMiliSeconds: 1000,
    numberOfRetries: 60,
    reaperInterval: 10000,
    reaperTimeout: 30000,
    readPreference: undefined },
 db: null,
 username: '',
 password: undefined,
 admin: { emitter: {}, state: 0, skinDb: [Circular], admin: null },
 _collections: { titles: [Circular] },
 bson_serializer:
  { BSON: [Object],
    Long: [Object],
    ObjectID: [Object],
    DBRef: [Function: DBRef],
    Code: [Function: Code],
    Timestamp: [Object],
    Binary: [Object],
    Double: [Function: Double],
    MaxKey: [Function: MaxKey],
    MinKey: [Function: MinKey],
    Symbol: [Function: Symbol] },
 ObjectID:
  { [Function: ObjectID]
    index: 0,
    createPk: [Function: createPk],
    createFromTime: [Function: createFromTime],
    createFromHexString: [Function: createFromHexString] } },
  ObjectID:
   { [Function: ObjectID]
 index: 0,
 createPk: [Function: createPk],
 createFromTime: [Function: createFromTime],
 createFromHexString: [Function: createFromHexString] },
  collectionName: 'titles',
  collection: null,
  internalHint: null,
  hint: [Getter/Setter] }

当我将console.log（）放在函数内部时，它工作得很好，我因某些原因无法返回字符串。

解决：

read = function(callback){
    titles.findOne(function(err, result){
        if (err) throw err;
        callback(result.title);
    });
};

read(function(title){
console.log(title);
});

Answer 1

你需要了解javascript回调。

1 - findOne将返回一个db对象，而不是字符串的结果。我从来没有读过mongoskin doco，但我认为这将是一个db集合或某种类型，你在console.log打印出来。 2 - 在回调中你做返回result.title;永远不会像你期望的那样返回标题。所以这就是为什么我建议阅读回调如何工作的原因。

打印标题的正确方法是将console.log放在回调函数中，如你所说。

使用mongoskin无法正确返回字符串

1 个答案: