No, that's not accurate - every `.then` always executes on a future tick,
never synchronously.
On Sat, Jul 27, 2019 at 11:11 PM Ranando King <king...@gmail.com> wrote:
> Isn't it always the case that `Promise.resolve()` returns an immediately
> resolved Promise? That means that the `.then` clause would get executed
> immediately as well, which is before you have a chance to set `this.foo`.
>
> Seems like what you need to do is something more like this:
> ```js
> // class Foo
> constructor() {
> (new Promise((resolve, reject) => { setTimeout(() => { resolve(); },1);
> })).then(() => {
> this.methodThatSubclassOverrides()
> })
> }
> ```
> Done this way, the call to `resolve()` will be thrown onto the run loop
> for execution later.
>
> On Sat, Jul 27, 2019 at 8:57 PM #!/JoePea <j...@trusktr.io> wrote:
>
>> I feel like I'm going crazy, but I have a class hierarchy, and one of
>> the constructors in the hierarchy defers some logic to a microtask,
>>
>> ```js
>> // class Foo
>> constructor() {
>> Promise.resolve().then(() => {
>> this.methodThatSubclassOverrides()
>> })
>> }
>>
>> methodThatSubclassOverrides() {}
>> ```
>>
>> and in the subclass there is
>>
>> ```js
>> // class Bar extends Foo
>> constructor() {
>> super()
>> this.foo = 123
>> }
>>
>> methodThatSubclassOverrides() {
>> console.log(this.foo) // should be "123"
>> }
>> ```
>>
>> You'd think the output should be "123" because the deferred code will
>> run after construction is complete.
>>
>> However, in my current project, the promise deferral seems to run
>> before the construction returns to the Bar constructor, thus this.foo
>> is not set, and calls `methodThatSubclassOverrides` before the Bar
>> class has a chance to run `this.foo = 123`. So the result of the
>> console.log is "undefined".
>>
>> It is totally weird. Do Promises ever resolve before a constructor
>> stack finishes?
>>
>> I don't have a simple reproduction at the moment.
>>
>> - Joe
>> _______________________________________________
>> es-discuss mailing list
>> es-discuss@mozilla.org
>> https://mail.mozilla.org/listinfo/es-discuss
>>
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