Order for async operations in js

Asked Oct 15 '17 at 14:18

Active Oct 15 '17 at 14:37

Viewed 100 times

Initially I have question about the order of number in code

(function() {
    setTimeout(() => console.log(1), 0);
    Promise.resolve(true).then(() => console.log(2));
})();

And for myself I've explained it like setTimeout uses 4ms in fact instead of 0.

But code works in same manner with setImmediate

(function() {
    setImmediate(() => console.log(1), 0);
    Promise.resolve(true).then(() => console.log(2));
})();

Man who asked the question said that the reason is the fact, that in v8 Promises is not part of webapis and run inside loops.

Maybe there are any other explanations? Or links to find more details?

If I use Loupe for visualization I see the same

Loupe visualization - I'm looking for explanation

edited Oct 15 '17 at 14:37

asked Oct 15 '17 at 14:18

3

There is no such function `setImmediate` maybe you've meant `setInterval`? – Krusader Oct 15 '17 at 14:20
1

Have you read through the extensive answer to [this question](https://stackoverflow.com/questions/36870467/what-is-the-order-of-execution-in-javascript-promises)? – Pointy Oct 15 '17 at 14:23
@Krusader [`setImmediate`](https://nodejs.org/api/all.html#globals_setimmediate_callback_args) is defined in Node.js. – str Oct 15 '17 at 14:25
OK now when you've added node.js tag it makes sense. – Krusader Oct 15 '17 at 14:26
@Krusader tag is there – Vasiliy vvscode Vanchuk Oct 15 '17 at 14:27
@Pointy if you're about the fact that Promises are async - I know it. Either I miss something in the answer? – Vasiliy vvscode Vanchuk Oct 15 '17 at 14:28
@Krusader setImmediate works in IE for example, not only node.js – Vasiliy vvscode Vanchuk Oct 15 '17 at 14:28
5

@VasiliyVanchuk it's asynchronous, but the relationship between Promise callbacks and timer callbacks is not specified and is left up to the runtime. It would be unwise to rely on any particular behavior. – Pointy Oct 15 '17 at 14:37

0 Answers0