WeakMap and WeakSet in ES6

Here we focus on the differences between them and the corresponding sets and maps.

• WeakSet

1. Cannot traverse, no forEach, no size
2. Only objects can be added
3. The garbage collector does not consider the WeakSet reference to the object at all.

• WeakMap

1. Keys can only be objects
2. The address where its key is stored does not affect garbage collection.

let obj ={
    
    
            name: 'Tom',
            age: 20
        }
 let map  = new WeakMap();
 obj = null; // 当obj设置为空之后，obj指向的这块内存地址就会被垃圾回收器回收
 console.log(map);

The printing results are as follows. We find that there are no key values ​​in the map.