The ES6 WeakMap and WeakSet classes
Along with the two new data structures Set
and Map
, ES6 also introduced a weak type version of these classes: WeakMap
and WeakSet
.
Basically, the only difference between the Map
or Set
classes and their Weak versions are:
- The
WeakSet
orWeakMap
classes do not have theentries
,keys
, andvalues
methods - It is only possible to use 0bjects as a key
The reason for creating and using these two classes is performance related. As WeakSet
and WeakMap
are weakly typed (using object as a key), there is no strong reference to the keys. This behavior allows the JavaScript garbage collector to clean an entire entry from the map or set.
Another advantage is that you can only retrieve a value if you have its key. As these classes ...
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