问题

{
"I'd like to simplify JSON object check for undefined values:": "我想简化对未定义值的 JSON 对象检查：",
"{\n body: {\n data: {\n names: [\n {\n firstName: 'John'\n },\n {\n firstName: 'Johnn'\n }\n ]\n }\n }\n}": " {\n body: {\n data: {\n names: [\n {\n firstName: 'John'\n },\n {\n firstName: 'Johnn'\n }\n ]\n }\n }\n}",
"So if I do it like this then it throws an exception if names is an empty array []:": "因此，如果我像这样做，如果 names 是一个空数组 []，它会引发异常：",
"body?.data?.names[0]?.firstName": "body?.data?.names[0]?.firstName",
"So should I go old way like this?": "那我应该像这样回到旧的方式吗？",
"if (\n body &&\n body.data &&\n body.data.names &&\n body.data.names.length > 0 &&\n body.data.names[0] &&\n body.data.names[0].firstName\n ) {": "if (\n body &&\n body.data &&\n body.data.names &&\n body.data.names.length > 0 &&\n body.data.names[0] &&\n body.data.names[0].firstName\n ) {",
"// ....\n}": "// ....\n}"
}

  {
    body: {
      data: {
        names: [
          {
            firstName: 'John'
          },
          {
            firstName: 'Johnn'
          }
        ]
      }
    }
  }

body?.data?.names[0]?.firstName

  if (
    body &&
    body.data &&
    body.data.names &&
    body.data.names.length > 0 &&
    body.data.names[0] &&
    body.data.names[0].firstName
  ) {
    // ....
  }

答案1

得分: 2

您可以尝试使用以下方式进行undefined检查，使用optional chaining (?.) 和 nullish coalescing (??) 运算符：

const data = {
    body: {
        data: {
            names: [
                {
                    firstName: 'John'
                },
                {
                    firstName: 'Johnn'
                }
            ]
        }
    }
};

// 测试
const firstName = data?.body?.data?.names?.[0]?.firstName ?? 'Unknown';

console.log(firstName); // 'John';

// 测试：未定义
const dataWithoutNames = {
    body: {
        data: {}
    }
};

const unknownName = dataWithoutNames?.body?.data?.names?.[0]?.firstName ?? 'Unknown';

console.log(unknownName); // 'Unknown';

const data =  {
    body: {
      data: {
        names: [
          {
            firstName: 'John'
          },
          {
            firstName: 'Johnn'
          }
        ]
      }
    }
  };

//test
const firstName = data?.body?.data?.names?.[0]?.firstName ?? 'Unknown';

console.log(firstName);//'John'

//test: undefined
const dataWithoutNames = {
  body: {
    data: {}
  }
};

const unknownName = dataWithoutNames?.body?.data?.names?.[0]?.firstName ?? 'Unknown';

console.log(unknownName);//'Unknown'