在没有父母的情况下获取所有子文档

Question

假设我具有以下JSON

{
    "name":"xpto",
    "assets":[{
        "name":"ypto",
        "orders":[{
            "client":"John",
        }],
        "dues": [{
            "refMonth":"01/2019",
        },{
            "refMonth":"02/2019",
        }]
    },
    {
        "name":"tpto",
        "orders":[{
            "client":"John",
        }],
        "dues": [{
            "refMonth":"01/2019",
        },{
            "baseDate":"02/2019",
        }]
    }]
}

我需要获取所有“ refMonth”字段，与父级无关。

我正在使用猫鼬，并且已经尝试过 MarketModel.findOne({"Name": req.params.market, "Assets.Name": req.params.asset}, callback)，但它带给我整个json