〖Vue3 源码笔记06〗WeakMap & WeakSet

// packages\reactivity\src\reactive.ts

// WeakMaps that store {raw <-> observed} pairs.
const rawToReactive = new WeakMap<any, any>()
const reactiveToRaw = new WeakMap<any, any>()
const rawToReadonly = new WeakMap<any, any>()
const readonlyToRaw = new WeakMap<any, any>()

function createReactiveObject(){
  ...
  observed = new Proxy(target, handlers)
  // 双缓存
  toProxy.set(target, observed)
  toRaw.set(observed, target)
  return observed
}

WeakMap

相比Map，WeakMap键只能为对象，且为弱引用，可以被回收，也因此无法确定当前还有多少key，即无法枚举。

听起来很像一个智能缓存

WeakMap	Map
set	set
get	get
has	has
delete	delete
	@@iterator
	clear
	keys
	values
	entries
	foreach

WeakSet

类似地，对象集合，无法枚举

WeakMap	Map
add	add
has	has
delete	delete
	@@iterator
	clear
	values
	entries
	foreach

拓展阅读

# ES6 系列之 WeakMap
# WeakMap 和 Map 的区别，WeakMap 原理，为什么能被 GC？
# 如何写出一个惊艳面试官的深拷贝?