带有投影以排除_id的Node.js MongoDB Find仍返回它 [英] Node.js MongoDB Find with projection to exclude _id still returns it

问题描述

尝试按照示例此处进行过滤，方法是使用排除_id的投影. _id仍然返回:

Trying to follow the examples here to filter by using a projection to exclude _id. The _id still returns:

代码

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/db1";

MongoClient.connect(url, function (err, db) {
    if (err) throw err;
    var dbase = db.db("db1"); //here    

    dbase.collection("customers").find(
        {},
        {
            _id: 0

        }
        ).toArray(function(err, result) {
        if (err) throw err;
        console.log(result);
        db.close();
    });

});

结果仍然返回如下:

[{_id:5a2bb2d6ee48575cb54c4365， 名称:约翰"， 地址:"Highway 71"}，{_id:5a2bb2d6ee48575cb54c436d， 名称:苏珊"， 地址:单向98")，.... {_id:5a2bb2d6ee48575cb54c4371， 名称:"Chuck"， 地址:"Main Road 989"}，{_id:5a2bb2d6ee48575cb54c4372， 名称:中提琴"， 地址:"Sideway 1633'}]

[ { _id: 5a2bb2d6ee48575cb54c4365, name: 'John', address: 'Highway 71' }, { _id: 5a2bb2d6ee48575cb54c436d, name: 'Susan', address: 'One way 98' }, .... { _id: 5a2bb2d6ee48575cb54c4371, name: 'Chuck', address: 'Main Road 989' }, { _id: 5a2bb2d6ee48575cb54c4372, name: 'Viola', address: 'Sideway 1633' } ]

从理论上讲，_id不应成为返回值的一部分.怎么了?

Theoretically _id should not be part of what is returned. What is wrong here?

推荐答案

要限制字段，您必须使用fields选项(不知道新更新):

To limit the fields you have to use fields option( dont know about new updates):

dbase.collection("customers").find(
        {},
        {fields:{_id: 0}}
        ).toArray(function(err, result) {
        if (err) throw err;
        console.log(result);
        db.close();
    });

更新:

对于版本3以上，您必须改用projection选项:

For version > 3 you have to use projection option instead:

dbase.collection("customers").find(
        {},
        {projection:{_id: 0}}
        ).toArray(function(err, result) {
        if (err) throw err;
        console.log(result);
        db.close();
    });

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