Question

我必须编写一个函数来检查参数1（firstName）是否是存储在变量（contacts）中的数组oj对象中的值，如果是，则返回当前对象的属性值（prop）。如果firstName不存在，我必须返回“未找到联系人”。如果找不到道具，我必须退回'没有这样的财产'。

我很难弄清楚如何检查在数组对象中是否找不到参数（firstName）。如何编写if语句来检查？

var contacts = [
  {
    "firstName": "Akira",
    "lastName": "Laine",
    "number": "0543236543",
    "likes": ["Pizza", "Coding", "Brownie Points"]
  },
  {
    "firstName": "Harry",
    "lastName": "Potter",
    "number": "0994372684",
    "likes": ["Hogwarts", "Magic", "Hagrid"]
  },
  {
    "firstName": "Sherlock",
    "lastName": "Holmes",
    'youtube': 'nah',
    "number": "0487345643",
    "likes": ["Intriguing Cases", "Violin"]
  },
  {
    "firstName": "Kristian",
    "lastName": "Vos",
    "number": "unknown",
    "likes": ["Javascript", "Gaming", "Foxes"]
  }
];

function lookUpProfile(firstName, prop){

  for (i=0;i<contacts.length;i++) {
    if (Object.values(contacts[i]).indexOf(firstName) > -1 && contacts[i].hasOwnProperty(prop)) {
      return contacts[i][prop];
  }
    if (!contacts[i].hasOwnProperty(prop)) {
      return 'No such property';
    }
  } 
}

lookUpProfile("Sherlock", "likes");

Answer 1

您使用Array.find查找具有正确firstName的对象。您可以按如下方式使用它：

function lookUpProfile(firstName, prop) {
    var profile = contacts.find(function(contact) {
        return contact.firstName === firstName;
    });

    if (!profile) {
        console.log("no profile found for " + firstName);
        return;
    }

    if (!profile[prop]) {
        console.log("no " + prop + " found on " + firstName + " profile");
        return;
    }

    return profile[prop];
}

Answer 2

＆＃13;

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<head>
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＆＃13;

Answer 3

＆＃13;

var check = (first, prop) => (obj.map(cur => cur.firstName === first ? cur.firstName : "Not found")[0]);

var obj = [{
 firstName: "Eduardo",
 age: 17
}];

console.log(check(obj[0].firstName));

＆＃13;

Answer 4

您当前的方法不允许区分这两个错误情况，因为您尝试将两个条件（名称和属性）组合在循环体内的单个if条件中。

此外，您的方法不允许lookUpProfile函数的用户区分真实错误和道具存在且具有值'No contact found'或'No such property'的特殊情况。你可能最好不要抛出异常而不是返回错误字符串。

一种工作方法是首先过滤具有匹配名称的候选人，然后找到具有所需属性的第一个候选人：

function lookUpProfile(firstName, prop) {
  const candidates = contacts.filter(contact => contact.firstName === firstName);
  if (candidates.length === 0) throw new Error('No contact found');
  const match = candidates.find(candidate => candidate.hasOwnProperty(prop));
  if (!match) throw new Error('No such property');
  return match[prop];
}

Answer 5

var contacts = [
  {
    "firstName": "Akira",
    "lastName": "Laine",
    "number": "0543236543",
    "likes": ["Pizza", "Coding", "Brownie Points"]
  },
  {
    "firstName": "Harry",
    "lastName": "Potter",
    "number": "0994372684",
    "likes": ["Hogwarts", "Magic", "Hagrid"]
  },
  {
    "firstName": "Sherlock",
    "lastName": "Holmes",
    'youtube': 'nah',
    "number": "0487345643",
    "likes": ["Intriguing Cases", "Violin"]
  },
  {
    "firstName": "Kristian",
    "lastName": "Vos",
    "number": "unknown",
    "likes": ["Javascript", "Gaming", "Foxes"]
  }
];

function lookUpProfile(firstName, prop){

  for (i=0;i<contacts.length;i++) {
    if (Object.values(contacts[i]).indexOf(firstName) > -1 && contacts[i].hasOwnProperty(prop)) {
      return contacts[i][prop];
  }
    if (!contacts[i].hasOwnProperty(prop)) {
      return 'No such property';
    }
  } 
}

lookUpProfile("Sherlock", "likes");

检查对象数组中是否不存在值

5 个答案: