如何在 JavaScript 中获取集合的长度

在 JavaScript 中获取集合的长度

How to get the Length of a Set in JavaScript

使用该size属性获取 Set 的长度，例如mySet.size. 该
size属性返回Set对象中值的数量。

当在空的上访问时Set，该size属性返回0。

const set = new Set(['a', 'b', 'c']);

console.log(set.size); // 👉️ 3

set.add('d');
set.add('e');

console.log(set.size); // 👉️ 5

我们使用
Set.size
属性来获取Set对象中元素的数量。

As opposed to the array’s length property, the size property is read-only
and can’t be changed by the user.

const set = new Set(['a', 'b', 'c']);

console.log(set.size); // 👉️ 3

set.size = 10;

console.log(set.size); // 👉️ 3

Even though we tried to update the size of the Set, we were unable to.

This is not the case when using the array’s length property.

const arr = ['a', 'b', 'c'];

console.log(arr.length); // 👉️ 3

arr.length = 10;

console.log(arr.length); // 👉️ 10

The code sample shows that we can update the array’s length and contents by
using its length property.

As expected, the size of the Set object is updated when:

• you add an element to the Set
• you remove an element from the Set
• you use the Set.clear() method to remove all elements from the Set

const set = new Set();

console.log(set.size); // 👉️ 0

// ✅ add elements to the Set
set.add('bobby');
set.add('hadz');

console.log(set.size); // 👉️ 2

// ✅ delete an element from the set
set.delete('bobby');

console.log(set.size); // 👉️ 1

// ✅ clear the set object
set.clear();

console.log(set.size); // 👉️ 0

We used the
Set.add
method to add 2 elements to the Set object.

Accessing the size property on the Set returns 2 at this point.

我们使用
Set.delete
方法从Set.

访问删除元素后size返回的属性。1

最后，我们使用
Set.clear
方法删除了 中的所有元素Set，因此该size属性返回
了0。