Question

//loping for objects

const users = [
    {isPremium: false},
    {isPremium: false},
    {isPremium: false},
    {isPremium: false},
    {isPremium: false},
  ]


function setUsersToPremium(users) {
  // users is an array of user objects.
  // each user object has the property 'isPremium'
  // set each user's isPremium property to true
  // return the users array
  for (let key in users) {
    users['isPremium'] = true;
  }
  return users;
}

setUsersToPremium(users);

我想知道如何遍历一个对象数组并将其值从false更改为true。这段代码的结果是

[true, true, true, true, true ]

但我想做的是改变每个

[isPremium: true]

我想知道我做了什么让我无法访问此值。

Answer 1

您必须设为users[key].isPremium = true;

//loping for objects

const users = [
   {isPremium: false},
   {isPremium: false},
   {isPremium: false},
   {isPremium: false},
   {isPremium: false},
]


function setUsersToPremium(users) {
  for (let key in users) {
    users[key].isPremium = true;
  }
  //return users; <-- No need to return. You are changing the user variable directly with these code.
}

setUsersToPremium(users);

console.log(users);

理想方法是使用forEach代替for/in

const users = [{isPremium: false},{isPremium: false},{isPremium: false},{isPremium: false},{isPremium: false},];

function setUsersToPremium(users) {
  users.forEach(o => o.isPremium = true);
}

setUsersToPremium(users);

console.log(users);

如果您不想影响原始数组，可以使用Object.assign

克隆该对象

const users = [{isPremium: false},{isPremium: false},{isPremium: false},{isPremium: false},{isPremium: false},];

function setUsersToPremium(users) {
  return users.map(o => {
    let x = Object.assign({}, o);
    x.isPremium = true;
    return x;
  });
}

var newUsers = setUsersToPremium(users);

console.log(newUsers);

Answer 2

您正在为数组使用for..in循环，因此您将获得array (1,2,3...)的索引

要解决此问题，您可以使用for..of循环

function setUsersToPremium(users) {
  for (let user of users) {
    user['isPremium'] = true;
  }
  return users;
}

Answer 3

您可以使用.map创建一个包含所需结果的新数组。

const users = [{
    isPremium: false
  },
  {
    isPremium: false
  },
  {
    isPremium: false
  },
  {
    isPremium: false
  },
  {
    isPremium: false
  },
]

const result = users.map(o => ({ isPremium: true}))
console.log(result)

Answer 4

const users = [{
  isPremium: false
}, {
  isPremium: false
}, {
  isPremium: false
}, {
  isPremium: false
}, {
  isPremium: false
}, ]
function setUsersToPremium(users) {
  // users is an array of user objects.
  // each user object has the property 'isPremium'
  // set each user's isPremium property to true
  // return the users array
  for (let key of users) {
    key.isPremium = true;
  }
  return users;
}

setUsersToPremium(users);

Answer 5

这也是一种不使用任何循环的简单方法。因为，您想要更改对象的所有isPremium属性的值，您可以对JSON数组进行字符串化，然后将false值替换为true，然后将其解析回数组。就这么简单：

const users = [
    {'isPremium': false},
    {'isPremium': false},
    {'isPremium': false},
    {'isPremium': false},
    {'isPremium': false},
];

var res = JSON.parse(JSON.stringify(users).replace(/false/g,'true'));

console.log(res);

Answer 6

const users = [
    {isPremium: false},
    {isPremium: false},
    {isPremium: false},
    {isPremium: false},
    {isPremium: false}
    ];


/** setUsersToPremium()
  * param: users, an array of objects
  * sets each user's isPremium property to true
  * returns users array
**/  
function setUsersToPremium() {
  for (let i = 0, max = users.length; i < max; i++) {
    users[i].isPremium = true;
  }
}

setUsersToPremium();
console.log(users);

几点说明：

不必将用户数组对象传递给函数也不行该函数需要返回此数组以实现所需的更改。
使用简单的for循环可能看起来很老套，但它仍然可以正常运行。

循环对象数组javascript

6 个答案: