When does an async task run in javascript?

Question

Suppose a javascript task makes an asynchronous call. e.g. xhr.send (material)

• Is (async) sending sent to another thread immediately? or
• Is the dispatch not sent before the completion of the current task?

I'm sure this is (2) the latter, but this behavior is covered by the specification or is it just a typical implementation. In the same vein ... Is creating a listener a synchronous call? Is there a specification covering this?

Answer 1

@Alnitak, fooobar.com/questions/163797/..., https://youtu.be/8aGhZQkoFbQ https://www.w3.org/TR/html51/webappapis.html#event-loops

, , , .

• () . [. xhr.send()]
• . [. xhr.addEventListener()]
• async , async
• .
• async , , .

async. https://chromium.googlesource.com/chromium/blink.git/+/99b8c9800ac123eddc3e199088d22569c5294b22/Source/core/xml/XMLHttpRequest.cpp

, , , dispatchEvent().