Because promise handlers aren’t immediately executed, you might imagine that they act a little like timers — giving the browser a chance to repaint and perform other important tasks before the handler is executed.
is this because callbacks go into the callback queue ie. lower priority than the microtask queue ?
promises and mutation observer go into the microtask queue and have higher higher priority, are DOM mutations the "important tasks" that James is refering to ??
In fact, promises aren’t like timers at all. If there are any promise handlers waiting to be executed when your script completes, they’ll be executed immediately.
is this because promises go into the microtask queue ( higher priority than the callback queue ) ??
rejection handler for then()
this is also applicable tor .catch() . since catch() is just a special case of .then() ie. .then(null , failure handler). Check the description of promise.catch in the "A Spoonful of Sugar" chapter.
An async function simply implies that a promise will be returned and if a promise is not returned, JavaScript will automatically wrap it in a resolved promise with the return value in that function. That would look like writing return Promise.resolve(‘hello’)