A question about async await with native promise.(try to implement zone.js for async/await)

[JiaLiPassion]

The following code

async function detect() { }
const r = detect();
const nativeThen = r.proto.then;
r.proto.then = function () {
console.log('promise.then');
return nativeThen.apply(this, arguments);
}

async function test1() {
console.log('before await');
const r = await test();
console.log('after await');
}

test1();
console.log('end');

// the output will be
// before await
// end
// promise.then, question is why promise.then is after end?
// after await
The nativePromise.then will be executed after end, I don't understand why, any help will be appreciated.

And What is the current status of zone proposal? Thanks!

[danielgindi]

This is because the Promise callbacks are always scheduled on the microtask queue. Which happens after the current execution context finishes.