用mongoose 查询获得的Decimal128数据，进行转化？

[ { "openValue":{ "$numberDecimal":"119.931" }, "timestamp":"2017-01-20T10:30:00.000Z" }, { "openValue":{ "$numberDecimal":"119.965" }, "timestamp":"2017-01-20T10:31:00.000Z" } ]，

怎样简单点转化为

[ { "openValue": 119.931, "timestamp":"2017-01-20T10:30:00.000Z" }, { "openValue": 119.965, "timestamp":"2017-01-20T10:31:00.000Z" }, { "openValue": 119.975, "timestamp":"2017-01-20T10:32:00.000Z" } ]