Node.js 如何在NodeJS中使用mongodb查询从多di数组中获取记录？

我是mongodb的新手，我想获取与u_id的条件等于特定u_id的记录相匹配的记录。我不清楚在哪里/应该应用什么条件来获取该特定记录

connection.model.find（{'abc.sar.0.u_id'：新ObjectID（'56e3e5b6fb33e53f11951f2'）），函数（err，result）{}

[
        {
          "_id": "56e15c49908fb5af0238f05c",
          "abc": {
            "sar": [
              {
                "u_id": "56e18c33909aa6f214e17dec",
                "cd": null,
                "_id": "56e18c33909aa6f214e17df0"
              },
              {
                "u_id": "56e18c4a909aa6f214e17df1",
                "cd": null,
                "_id": "56e18c4a909aa6f214e17df5"
              },
              {
                "u_id": "56e18f6a909aa6f214e17df6",
                "cd": null,
                "_id": "56e18f6a909aa6f214e17dfa"
              },
              {
                "u_id": "56e3c477a8b75d720c73e5a7",
                "cd": null,
                "_id": "56e3c477a8b75d720c73e5ab"
              },
              {
                "u_id": "56e3e5b6fb33e53f119051f2",
                "cd": null,
                "_id": "56e3e5b6fb33e53f119051f6"
              },
              {
                "u_id": "56e3e60efb33e53f119051f7",
                "cd": null,
                "_id": "56e3e60efb33e53f119051fb"
              },
              {
                "u_id": "56e3eaedc0e2dba711805f0e",
                "cd": null,
                "_id": "56e3eaedc0e2dba711805f12"
              },
              {
                "u_id": "56e3eb85f81fe30d12507709",
                "cd": null,
                "_id": "56e3eb86f81fe30d1250770d"
              }
            ]
          }
        }
      ]

你想用

connection.model.find({
    'abc.sar' : { 
        $elemMatch : {'u_id': new ObjectID( '56e3e5b6fb33e53f119051f2' )}
    }
});