weakmap

Why will ES6 WeakMap's not be enumerable?

由 南笙酒味 提交于 2020-01-09 07:15:29
问题 Before my re-entry in JavaScript (and related) I've done lots of ActionScript 3 and there they had a Dictionary object that had weak keys just like the upcoming WeakMap; but the AS3 version still was enumerable like a regular generic object while the WeakMap specifically has no .keys() or .values() . The AS3 version allowed us to rig some really interesting and usefull constructs but I feel the JS version is somewhat limited. Why is that? If the Flash VM could do it then what is keeping

Why will ES6 WeakMap's not be enumerable?

由 笑着哭i 提交于 2020-01-09 07:15:01
问题 Before my re-entry in JavaScript (and related) I've done lots of ActionScript 3 and there they had a Dictionary object that had weak keys just like the upcoming WeakMap; but the AS3 version still was enumerable like a regular generic object while the WeakMap specifically has no .keys() or .values() . The AS3 version allowed us to rig some really interesting and usefull constructs but I feel the JS version is somewhat limited. Why is that? If the Flash VM could do it then what is keeping

Would a “circular” reference be treated as “reachability” for a WeakMap?

由 一世执手 提交于 2019-12-21 09:29:10
问题 function f() { const w = new WeakMap(); const o = {}; w.set(o, { v: o }); return w; } const weakMap = f(); For the given code, would the only weakMap item considered as reachable or not? Hence, will it be garbage collected or not? PS: This question is asked from the perspective of the specification, not particular implementations. 回答1: Quoting WeakMap Objects section, If an object that is being used as the key of a WeakMap key/value pair is only reachable by following a chain of references

Would a “circular” reference be treated as “reachability” for a WeakMap?

由 拈花ヽ惹草 提交于 2019-12-21 09:28:02
问题 function f() { const w = new WeakMap(); const o = {}; w.set(o, { v: o }); return w; } const weakMap = f(); For the given code, would the only weakMap item considered as reachable or not? Hence, will it be garbage collected or not? PS: This question is asked from the perspective of the specification, not particular implementations. 回答1: Quoting WeakMap Objects section, If an object that is being used as the key of a WeakMap key/value pair is only reachable by following a chain of references

How to iterate over a weakmap?

由 房东的猫 提交于 2019-12-18 05:39:04
问题 A javascript WeakMap ( https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakMap ) does not allow you to get the key, or the length or size, by design. Is it possible to nevertheless loop over entries in some way ? If not .. how does the Chrome console do this ? 回答1: Is it possible to nevertheless loop over entries in some way? No, as you say, the contents of a WeakMap are not accessible by design, and there is no iterability. If not … how does the Chrome

What's the difference between ES6 Map and WeakMap?

由 馋奶兔 提交于 2019-12-17 07:04:29
问题 Looking this and this MDN pages it seems like the only difference between Maps and WeakMaps is a missing "size" property for WeakMaps. But is this true? What's the difference between them? 回答1: From the very same page, section "Why Weak Map?": The experienced JavaScript programmer will notice that this API could be implemented in JavaScript with two arrays (one for keys, one for values) shared by the 4 API methods. Such an implementation would have two main inconveniences. The first one is an

What's the difference between ES6 Map and WeakMap?

由 六月ゝ 毕业季﹏ 提交于 2019-12-13 02:43:40
问题 Looking this and this MDN pages it seems like the only difference between Maps and WeakMaps is a missing "size" property for WeakMaps. But is this true? What's the difference between them? 回答1: From the very same page, section "Why Weak Map?": The experienced JavaScript programmer will notice that this API could be implemented in JavaScript with two arrays (one for keys, one for values) shared by the 4 API methods. Such an implementation would have two main inconveniences. The first one is an

JavaScript WeakMap keep referencing gc'ed objects

由 时间秒杀一切 提交于 2019-12-04 03:36:21
问题 I am experiencing with JavaScript weakmaps, after trying this code in google chrome developer console, running with --js-flags="--expose-gc", I don't understand why the weakmap keep having a reference to a.b if a is gc'ed. var a = {listener: function(){ console.log('A') }} a.b = {listener: function(){ console.log('B') }} var map = new WeakMap() map.set(a.b, []) map.set(a, [a.b.listener]) console.log(map) // has both a and a.b gc() console.log(map) // still have both a and a.b a = undefined gc

JavaScript WeakMap keep referencing gc'ed objects

由 ￡可爱￡侵袭症＋ 提交于 2019-12-01 18:54:51
I am experiencing with JavaScript weakmaps, after trying this code in google chrome developer console, running with --js-flags="--expose-gc", I don't understand why the weakmap keep having a reference to a.b if a is gc'ed. var a = {listener: function(){ console.log('A') }} a.b = {listener: function(){ console.log('B') }} var map = new WeakMap() map.set(a.b, []) map.set(a, [a.b.listener]) console.log(map) // has both a and a.b gc() console.log(map) // still have both a and a.b a = undefined gc() console.log(map) // only have a.b: why does still have a reference to a.b? Should'nt be erased? In

How to iterate over a weakmap?

由 随声附和 提交于 2019-11-29 09:15:47
A javascript WeakMap ( https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakMap ) does not allow you to get the key, or the length or size, by design. Is it possible to nevertheless loop over entries in some way ? If not .. how does the Chrome console do this ? Is it possible to nevertheless loop over entries in some way? No, as you say, the contents of a WeakMap are not accessible by design, and there is no iterability. If not … how does the Chrome console do this? The console uses the debugging API of the JS engine, which allows access to the internals of
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