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问JQuery检查JSON数据是否包含某个键
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Stack Overflow用户

提问于 2020-06-26 21:09:52

回答 2查看 26关注 0票数 0

因此，我尝试检查某些JSON数据是否包含某个键，如果包含，则显示该键值，但我一直收到错误"TypeError: Cannot read property 'CurrentTextValue' of undefined

如何检查某个键是否存在，以及它是否显示其值。

var carj = '[{ "Description": "SAAB 900 S CONVERTIBLE", "RegistrationYear": "1993", "CarMake": { "CurrentTextValue": "SAAB" }, "CarModel": { "CurrentTextValue": "900 S CONVERTIBLE" }, "MakeDescription": { "CurrentTextValue": "SAAB" }, "ModelDescription": { "CurrentTextValue": "900 S CONVERTIBLE" }, "EngineSize": { "CurrentTextValue": "1985" }, "BodyStyle": { "CurrentTextValue": "Motorbike" }, "FuelType": { "CurrentTextValue": "PETROL" }, "Variant": "", "Colour": "BLACK", "VehicleIdentificationNumber": "YS3AD75S1P7004905", "KType": "", "EngineNumber": "B202S3M03P032338" }]';

carj2 = $.parseJSON(carj);

if(carj2[0].NumberOfDoors.CurrentTextValue != '') {
console.log(carj2[0].NumberOfDoors.CurrentTextValue);
} else {
console.log('i dont have doors');
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

javascript

jquery

回答 2

Stack Overflow用户

发布于 2020-06-26 21:14:32

您需要首先找到NumberOfDoors，然后再查找值

在这里，我使用一个三元运算符作为输出

const carj = '[{ "Description": "SAAB 900 S CONVERTIBLE", "RegistrationYear": "1993", "CarMake": { "CurrentTextValue": "SAAB" }, "CarModel": { "CurrentTextValue": "900 S CONVERTIBLE" }, "MakeDescription": { "CurrentTextValue": "SAAB" }, "ModelDescription": { "CurrentTextValue": "900 S CONVERTIBLE" }, "EngineSize": { "CurrentTextValue": "1985" }, "BodyStyle": { "CurrentTextValue": "Motorbike" }, "FuelType": { "CurrentTextValue": "PETROL" }, "Variant": "", "Colour": "BLACK", "VehicleIdentificationNumber": "YS3AD75S1P7004905", "KType": "", "EngineNumber": "B202S3M03P032338" }]';


const carj2 = $.parseJSON(carj);

const NumberOfDoors = carj2[0].NumberOfDoors;
console.log( NumberOfDoors ? NumberOfDoors.CurrentTextValue : 'I don\'t have doors');

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

2020年最新的JS可以做Optional Chaining

注意["NumberOfDoors"]?中的?

const carj = '[{ "Description": "SAAB 900 S CONVERTIBLE", "RegistrationYear": "1993", "CarMake": { "CurrentTextValue": "SAAB" }, "CarModel": { "CurrentTextValue": "900 S CONVERTIBLE" }, "MakeDescription": { "CurrentTextValue": "SAAB" }, "ModelDescription": { "CurrentTextValue": "900 S CONVERTIBLE" }, "EngineSize": { "CurrentTextValue": "1985" }, "BodyStyle": { "CurrentTextValue": "Motorbike" }, "FuelType": { "CurrentTextValue": "PETROL" }, "Variant": "", "Colour": "BLACK", "VehicleIdentificationNumber": "YS3AD75S1P7004905", "KType": "", "EngineNumber": "B202S3M03P032338" }]';


const carj2 = $.parseJSON(carj);

const NumberOfDoors = carj2[0].NumberOfDoors?.CurrentTextValue || 0
console.log(NumberOfDoors ||  'I don\'t have doors');

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

票数 0

Stack Overflow用户

发布于 2020-06-26 21:23:19

var carj = '[{ "Description": "SAAB 900 S CONVERTIBLE", "RegistrationYear": "1993", "CarMake": { "CurrentTextValue": "SAAB" }, "CarModel": { "CurrentTextValue": "900 S CONVERTIBLE" }, "MakeDescription": { "CurrentTextValue": "SAAB" }, "ModelDescription": { "CurrentTextValue": "900 S CONVERTIBLE" }, "EngineSize": { "CurrentTextValue": "1985" }, "BodyStyle": { "CurrentTextValue": "Motorbike" }, "FuelType": { "CurrentTextValue": "PETROL" }, "Variant": "", "Colour": "BLACK", "VehicleIdentificationNumber": "YS3AD75S1P7004905", "KType": "", "EngineNumber": "B202S3M03P032338" }]';

carj2 = $.parseJSON(carj);

// Method 1
if ("numberOfDoors" in carj2[0]) {
    console.log(carj2[0].NumberOfDoors.CurrentTextValue);
} else {
    console.log('i dont have doors');
}

// Method 2
console.log(carj2[0].NumberOfDoors?.CurrentTextValue || "i dont have doors");

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

“in”运算符可用于检查对象是否包含某个键。那个？运算符还可用于确保JavaScript不会尝试获取和使用未定义的值。

票数 0

页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持

原文链接：

https://stackoverflow.com/questions/62595448

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