| Feature Comparison | Set | WeakSet | Map | WeakMap |
|---|---|---|---|---|
| Initialization | new Set([1,2,3,4]) | new WeakSet([1,2,3,4]) | new Map([["name", "Bright"], ["sex", "男"]]) | new WeakMap([["name", "Bright"], [" sex", "男"]]) |
| Definition | An ordered list containing multiple non-duplicate values | A special Set collection that only supports storing weak references to objects | An ordered collection of multiple key-value pairs | A special Map collection that only supports object-type keys |
| Iterable | Yes | No | Yes | No |
| Reference Feature | Member objects strong reference | Member objects weak reference | Member objects strong reference | Member objects weak reference |
| Properties & Methods | add() has() delete() clear() forEach() keys() values() size | add() has() delete() | set() get() has() delete() clear() forEach() keys() values() size | set () get() has() delete() |
| Usage Recommendation | Due to the limitations of object property existence detection, this collection is more suitable for detecting whether a given value exists in the collection. Based on its non-duplicate value feature, it can be used for array deduplication | Can only store object types and facilitates tracking of referenced objects | Used for handling key-value pair data, storing data that needs frequent access | Used for handling key-value pair data, keys can only store object types, and facilitates tracking of referenced objects. The main use is to save DOM elements of web pages |
Iterable#
Whether iterable is used to indicate whether the collection supports traversing member properties, including the use of methods such as forEach(), keys(), values(), for…of, etc.
Object Limitations#
Using if in objects to determine whether a value exists is not rigorous enough. When the property itself doesn’t exist and exists with a value of false, the judgment results are the same, which brings problems. There’s another method to determine whether a property exists in an object using ‘in’, but this method will traverse up the inherited prototype properties, also bringing some unknown problems, unless the object inherits from null.
Strong Reference#
As long as the reference exists, the garbage collection mechanism will not release the memory space of the referenced object.
Weak Reference#
When the referenced object is set to null, the collection doesn’t save the reference, triggering the garbage collection mechanism.