Object.keys（）

`Object.keys()` 是JavaScript内置的一个方法，它接收一个对象作为参数，并返回该对象的所有自身可枚举属性的名称组成的数组。这个数组包含了对象的键，而不是值。例如，如果你有一个对象：

const person = {
  name: "Alice",
  age: 30,
  city: "New York"
};

使用 `Object.keys(person)`，你会得到一个包含 ["name", "age", "city"] 的数组，表示 `person` 对象的所有属性名。

这个方法常用于遍历对象、检查某个对象是否有特定的属性，或者获取对象属性名列表，以便进一步操作或处理这些属性。例如：

// 遍历并打印对象的所有属性名
for (let key of Object.keys(person)) {
  console.log(key);
}

// 检查对象是否存在某个属性
if (Object.keys(person).includes("age")) {
  console.log("Age is a property");
}

相关问题

Object.keys

Object.keys() is a method in JavaScript that returns an array of a given object's own property names. It takes the object as an argument and returns an array of strings containing the property names. The order of the property names in the array is the order in which they were added to the object. The method does not include any properties from the object's prototype chain.

object.keys

Object.keys() is a built-in JavaScript method that returns an array of the object's property names. It takes an object as an argument and returns an array of the property names of that object. The returned array contains only the property names that are directly owned by the object and not inherited from its prototype chain. The order of the property names in the array is not guaranteed and may vary depending on the JavaScript engine.

For example, consider the following object:

const person = {
  firstName: 'John',
  lastName: 'Doe',
  age: 30,
  email: 'john.doe@example.com'
};

We can use Object.keys() to get an array of the property names of the person object:

const keys = Object.keys(person);
console.log(keys); // Output: ['firstName', 'lastName', 'age', 'email']

We can then use this array to loop through the object's properties, or access a specific property using bracket notation:

keys.forEach(key => {
  console.log(person[key]); // Output: 'John', 'Doe', 30, 'john.doe@example.com'
});

console.log(person[keys[0]]); // Output: 'John'