Javascript JSON对象中缺少模型属性

我有3种型号：

export class Period {
    lifeYears: number;
    lifeDevelopment: number;
}

export class PairYearQuantity {
    id: number;
    year: number;
    quantity: number;
}

export class MarketingPhase {
    status: string;
    period: Period;
    investments: PairYearQuantity[];
    costs: PairYearQuantity[];
}

我创建了一个对象，如下所示：

const marketingPhase: MarketingPhase = {
    status: 'empty',
    period: {
        lifeYears: 3,
        lifeDevelopment: 2
    },
    investments: [
        {
            id: 1,
            year: 2018,
            quantity: 15
        },
        {
            id: 2,
            year: 2019,
            quantity: 8
        }
    ],
    costs: [
        {
            id: 7,
            year: 2018,
            quantity: 21
        },
        {
            id: 8,
            year: 2019,
            quantity: 13
        }
    ]
};

如果我在控制台中打印对象，“id”属性丢失，“quantity”的值为空。似乎PairYearQuantity模型不太适用

console.log(marketingPhase);

结果是：

{
    status: 'empty',
    period: {
        lifeYears: 3,
        lifeDevelopment: 2
    },
    investments: [
        {
            year: 2018,
            quantity: null
        },
        {
            year: 2019,
            quantity: null
        }
    ],
    costs: [
        {
            year: 2018,
            quantity: null
        },
        {
            year: 2019,
            quantity: null
        }
    ]
}

但是如果我打印例如

console.log（marketingPhase.investments[0].quantity）我得到
15

你知道这是怎么回事，怎么解决吗？
你在什么地方修改了
marketingPhase
？我检查它是否正常工作。请参阅，您的模型不应该有问题，因为它们只是类型脚本类。你能提供你的代码的更多细节吗？也许是一把小木棍或一把小提琴。