使用 JavaScript 检查集合中是否包含某个值
使用 has() 方法检查 Set 是否包含值，例如 set.has(1)。 如果该值包含在 Set 中，则 has() 方法返回 true，否则返回 false。
const set1 = new Set(['one', 'two', 'three']);
console.log(set1.has('one')); // 👉️ true
console.log(set1.has('four')); // 👉️ false
Set.has() 方法采用的唯一参数是我们要测试是否存在于 Set 中的值。
has 方法返回一个布尔结果：
- 如果值包含在 Set 中则为真
- 如果值不在集合中则为 false
这里还有一些例子。
const set1 = new Set();
const obj = {country: 'Chile'};
set1.add(obj);
console.log(set1.has(obj)); // 👉️ true
const arr = ['one', 'two'];
set1.add(arr);
console.log(set1.has(arr)); // 👉️ true
// 👇️ false because they reference
// different locations in memory
console.log(set1.has(['one', 'two']));
set1.delete(arr);
console.log(set1.has(arr)); // 👉️ false
has() 方法甚至适用于对象和数组，只要它们具有相同的引用即可。
has() 方法不检查对象或数组的值是否相等，而是检查它们是否引用内存中的相同位置。
const obj = {};
console.log(obj === obj); // 👉️ true
console.log({} === {}); // 👉️ false
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