节点js Array.push（）无法使用猫鼬

Question

I am beginner in meanstack development. I am trying to push value inside an array in foreach loop but last i am getting empty array.

My code:

router.get("/", function(req, res) {

 ourpackage.find({}).sort({_id:1}).exec(function(err,resdoc){

  var rest = [];
  resdoc.forEach(function(doc){
    masterRoomimage.find({ourpackageId:doc._id},function(err,ourpackageimagevalue){
      if(err) res.send(err);
      var ourpackagedetail = JSON.parse(JSON.stringify(doc));
      var stringifyimages = JSON.parse(JSON.stringify(ourpackageimagevalue));
      var ourpackage = _.merge({},ourpackagedetail,{masterRoomimages:stringifyimages});
      rest.push(ourpackageimagevalue);
             //print all rest array value
             console.log(rest);
           });
  });
      //print empty rest array value
      console.log(rest);
      res.send(rest);
    });
});

ourpackage Schema

  {
            "_id": "58e396d4215bc61338d2c06e",
            "first_title": "test 1",
            "berief_text": "<p>testing </p>",
   }

ourpackagesimages Schema

[
            {
                "_id": "59424d49fcc8100050916bf4",
                "imageLocation": "first.jpg",
                "ourpackageId": "58e396d4215bc61338d2c06e",
                "__v": 0
            },
            {
                "_id": "59424d49fcc8100050916bf5",
                "imageLocation": "third.jpg",
                "ourpackageId": "58e396d4215bc61338d2c077",
                "__v": 0
            },
            {
                "_id": "59490ad44e26c13324906433",
                "imageLocation": "second.jpg",
                "ourpackageId": "58e396d4215bc61338d2c06e",
                "__v": 0
            }
    ]

expected output

[
    {
        "_id": "58e396d4215bc61338d2c06e",
        "first_title": "test 1",
        "berief_text": "<p>testing </p>",
        "ourpackagesimages": [
            {
                "_id": "59424d49fcc8100050916bf4",
                "imageLocation": "first.jpg",
                "ourpackageId": "58e396d4215bc61338d2c06e",
                "__v": 0
            },
            {
                "_id": "59490ad44e26c13324906433",
                "imageLocation": "second.jpg",
                "ourpackageId": "58e396d4215bc61338d2c06e",
                "__v": 0
            }

        ]
    }
]

obtained output empty

[]

Answer 1

You can't call an asynchronous function inside a synchronous function ( forEach in this case). The result is accessed before it's collected and that's why the empty array output.

A very handy and easy to use library for this purpose is async . For your particular use case, map or mapLimit function will do.

var async = require('async');

router.get("/", function(req, res) {
    ourpackage.find({}).sort({
        _id: 1
    }).exec(function(err, resdoc) {

        async.mapLimit(resdoc, 5, function(doc, callback){
            masterRoomimage.find({
                ourpackageId: doc._id
            }, function(err, ourpackageimagevalue) {
                if (err) return callback(err);

                var ourpackagedetail = JSON.parse(JSON.stringify(doc));
                var stringifyimages = JSON.parse(JSON.stringify(ourpackageimagevalue));
                var ourpackage = _.merge({}, ourpackagedetail, {
                    masterRoomimages: stringifyimages
                });
                return callback(null, ourpackageimagevalue);
            });

        }, function(err, rest) {
            if(err){
                res.send(err);
            }
            else{
                res.send(rest);
            }
        });
    });
});

Answer 2

simply, Declare an array rest = [];

rest[] = ourpackageimagevalue;

I hope it helps,