javascript - 如何同步确定JavaScript Promise的状态？(How can I synchronously determine a JavaScript Promise's state?)

Question

I have a pure JavaScript Promise (built-in implementation or poly-fill):

(我有一个纯JavaScript Promise（内置实现或poly-fill）：)

var promise = new Promise(function (resolve, reject) { /* ... */ });

From the specification , a Promise can be one of:

(根据规范 ，Promise可以是以下之一：)

• 'settled' and 'resolved'

  (“解决”和“解决”)

• 'settled' and 'rejected'

  (“解决”和“拒绝”)

• 'pending'

  (“待定”)

I have a use case where I wish to interrogate the Promise synchronously and determine:

(我有一个用例，希望同步查询Promise并确定：)

• is the Promise settled?

  (承诺解决了吗？)

• if so, is the Promise resolved?

  (如果是这样，承诺是否得到解决？)

I know that I can use #then() to schedule work to be performed asynchronously after the Promise changes state.

(我知道可以在Promise更改状态后使用#then()安排要异步执行的工作。)

I am NOT asking how to do this.

(我不是问怎么做。)

This question is specifically about synchronous interrogation of a Promise's state .

(这个问题专门关于无条件状态的同步询问 。)

How can I achieve this?

(我该如何实现？)

  ask by jokeyrhyme translate from so

Answer 1

No such synchronous inspection API exists for native JavaScript promises.

(不存在用于本机JavaScript承诺的此类同步检查API。)

It is impossible to do this with native promises.

(凭本地承诺是不可能做到这一点的。)

The specification does not specify such a method.

(规范未指定这种方法。)

Userland libraries can do this, and if you're targeting a specific engine (like v8) and have access to platform code (that is, you can write code in core ) then you can use specific tools (like private symbols) to achieve this.

(Userland库可以做到这一点，如果您要针对特定??的引擎（例如v8）并有权访问平台代码 （即可以在core中编写代码），则可以使用特定的工具（例如私有符号）来实现这一目标。 。)

That's super specific though and not in userland.

(这是非常具体的，但不是在用户领域。)