Question

需要一些节点js和mongodb的帮助我该怎么回复？因为它现在返回＆＃34; undefined＆＃34 ;;

function(table, where, to_select) {
  var r = {};
  MongoClient.connect("mongodb://127.0.0.1:27017/db", function(err, db) {
    if(!err) {
      collection = db.collection(table);
      collection.find(where, to_select).toArray(function(err, resp) {
        r.t = resp; // return THIS
      });
    }
  });
  return r.t; //returns undefined //
}

Answer 1

MongoClient.connect＆amp; collection.find是asynchronous个函数。要正确获得resp的价值，您可以将getData函数asynchronous设为如下所示。

function getData(table, where, to_select, callback) { // We pass callback function 
    var r = {};
    MongoClient.connect("mongodb://127.0.0.1:27017/db", function(err, db) {
        if (!err) {
            collection = db.collection(table);
            collection.find(where, to_select).toArray(function(err, resp) {
             // r.t = resp; no need to assign as you want resp only
             callback(err,resp); // return resp
            })
        }else
           callback(err);// return with error 
    });
    //return r.t; r.t will be undefined as r.t is not updated yet, so we can remove this
}


/*Now you can call as below
  getData(whatever,)whatever,whatever,function(err,resp){
      console.log(resp);// You will get result here
  })*/

Answer 2

您需要使用回调，因为异步操作中的DB查询。所以在查找实际返回结果之前会调用您的返回。这是修复

beforeConnect: function(handshake, cb) { if (handshake.headers.cookie) { console.log(handshake); // TODO: check session authorization } else { return cb(null, false); } return cb(null, true); },

要调用你需要的功能

function runQuery(table,where,to_select, callback){
  MongoClient.connect("mongodb://127.0.0.1:27017/db", function(err, db) {
        if (err) {return callback(err);}
        collection = db.collection(table);
        collection.find(where,to_select).toArray(function(err, resp) {
            callback(err, resp);
        });
  }); 
}

希望这有帮助。

使用mongodb函数中的字符串

2 个答案: