Node.js：indexOf返回-1，即使item在数组中

Question

我希望用户能够单击一个按钮，将用户名和id推送到与数据库中的集合关联的数组中，但前提是它们不在该数组中。

我的解决方案是：

var isInGroup = function(user, arr){

    var match = arr.indexOf(user);
    console.log(">>>>>>>" + match);
    if(match === -1){
        arr.push(user);
        console.log("added user");

    } else {
        console.log("Already in group");
    }
};

当我在控制台中对示例数组进行测试时，这是有效的，但在我查询数据库时却没有。当我在我的应用程序中执行该函数时，即使用户已经在数组中，arr.indexOf = -1。

这是相关代码：

Player.js

var express = require("express"),
    router = express.Router({mergeParams:true}),
    Game = require("../models/game"),
    Player = require("../models/player"),
    User = require("../models/user"),
    middleware = require("../middleware");


//Add A Player 
router.post("/", middleware.isLoggedIn, function(req, res){
    //find game
    Game.findById(req.body.game, function(err, foundGame){
        console.log(">>>>" + foundGame);
         if(err){
            req.flash("error", "Something went wrong.");  
      }  else {
          //create player
          Player.create(req.user, function(err, player){
              if(err){
                  console.log(">>>> error" + player);
                  res.redirect("back");
              } else {

                  player.id = req.user_id;
                  player.username = req.user.username;
                  middleware.isInGroup(player, foundGame.players);

                  foundGame.save();
                  res.redirect("back");
              }
          });
        }
    });
});

游戏架构

var mongoose = require("mongoose");

var gameSchema = new mongoose.Schema({
    name:String,
    author:{
        id:{
            type: mongoose.Schema.Types.ObjectId,
            ref:"User"
        },
        username:String,
    },
    court:{
        id:{
            type:mongoose.Schema.Types.ObjectId,
            ref:"Court"
        },
        name:String,
    },
    players:[
        {
            id:{    type:mongoose.Schema.Types.ObjectId,
            ref:"Player",
            },
            username:String
            }


    ],
    time:{
        start:String,
        end:String
    },
    date:String,
});

module.exports = mongoose.model("Game", gameSchema)

播放器架构

var mongoose = require("mongoose");

var playerSchema = new mongoose.Schema({

        id:{type:mongoose.Schema.Types.ObjectId,
        ref:"User" 
        },
        username: String

});

module.exports = mongoose.model("Player", playerSchema);

User Schema
var mongoose              = require("mongoose"),
    passportLocalMongoose = require("passport-local-mongoose");

var userSchema = new mongoose.Schema({
    username: String,
    password: String
});

userSchema.plugin(passportLocalMongoose);

module.exports = mongoose.model("User", userSchema);

如上所述，即使用户已经在数组中，arr.indexOf（user）也会返回-1。为什么会这样？这个问题有更好的解决方案吗？谢谢您的帮助。我一直在敲打这个问题。