[ { "vehicleId": "34b8413a541612cfdb53a35e00f2b17c", "vehicleCode": "京AF03128", "brandId": "福田", "vehicleVin": "LVBV3J0B0NW001886", "engineCode": null, "drivingSignDate": "2022-06-14 00:00:00", "createTime": "2022-11-16 23:44:58", "yxnEquipmentCode": null, "yxnSn": null, "signType": "046001", "signFlag": 1, "billPrice": 0, "signMileage": 0, "mileageCurrent": 0, "mileageLast": 0, "signStartTime": "2023-03-01 00:00:00" } ],修改上述数据结构，添加一个total属性，如果mileageLast=0，total的值为signMileage乘以billPrice，如果mileageLast不是0，total的值为mileageCurrent减去mileageLast乘以billPrice 前端 es6

你可以使用ES6的箭头函数和条件运算符来实现这个需求。以下是修改后的数据结构的示例代码：

const data = [
    {
        "vehicleId": "34b8413a541612cfdb53a35e00f2b17c",
        "vehicleCode": "京AF03128",
        "brandId": "福田",
        "vehicleVin": "LVBV3J0B0NW001886",
        "engineCode": null,
        "drivingSignDate": "2022-06-14 00:00:00",
        "createTime": "2022-11-16 23:44:58",
        "yxnEquipmentCode": null,
        "yxnSn": null,
        "signType": "046001",
        "signFlag": 1,
        "billPrice": 0,
        "signMileage": 0,
        "mileageCurrent": 0,
        "mileageLast": 0,
        "signStartTime": "2023-03-01 00:00:00"
    }
];

const modifiedData = data.map(item => ({
    ...item,
    total: item.mileageLast === 0 ? item.signMileage * item.billPrice : (item.mileageCurrent - item.mileageLast) * item.billPrice
}));

console.log(modifiedData);

在上述代码中，使用`map`方法遍历原始数据数组，并使用对象扩展运算符`...`将原始对象的所有属性复制到新对象中。然后，根据`mileageLast`的值使用条件运算符来计算`total`属性的值，并将新对象添加到`modifiedData`数组中。

请注意，这只是一个示例代码，你需要根据你的实际情况进行相应的调整。