javascript - 如何检查对象的属性值？

Question

我需要查找属性在对象中具有特定值的次数。

对象:

let users = {
  Alan: {
    age: 27,
    online: false
  },
  Jeff: {
    age: 32,
    online: true
  },
  Ryan: {
    age: 19,
    online: true
  }
};

我需要查找有多少在线值为 true

到目前为止我尝试过的:

function countOnline(obj) {
  let count = 0;
    for (let user in obj) {
      if (obj.user == true) {
      count++;
      }
    }
  return count;
}

console.log(countOnline(users)); // 0
console.log(users.Ryan.online); // true

console.log(countOnline(users)); // should return 2 as the number of online: true exists twice

Answer 1

我会减少对象的Object.values，当online为true时增加累加器:

let users = {
  Alan: {
    age: 27,
    online: false
  },
  Jeff: {
    age: 32,
    online: true
  },
  Ryan: {
    age: 19,
    online: true
  }
};

const onlineCount = Object.values(users).reduce((a, { online }) => a + online, 0);
console.log(onlineCount);

要修复现有代码，请将测试更改为 obj[user].online === true (或只是 obj[user].online):

let users = {
  Alan: {
    age: 27,
    online: false
  },
  Jeff: {
    age: 32,
    online: true
  },
  Ryan: {
    age: 19,
    online: true
  }
};

function countOnline(obj) {
  let count = 0;
  for (let user in obj) {
    if (obj[user].online === true) {
      count++;
    }
  }
  return count;
}

console.log(countOnline(users));