Why do Promise libraries use event loops?

Question

Considering the following JavaScript code:

var promise = new Promise();
setTimeout(function() {
    promise.resolve();
}, 10);

function foo() { }
promise.th         


        

Answer 1

Promises are all about cooperative multitasking.

Pretty much the only method to achieve that is to use message based scheduling.

Timers (usually with 0 delay) are simply used to post the task/message into message queue - yield-to-next-task-in-the-queue paradigm. So the whole formation consisting of small event handlers works and more frequently you yield - more smoothly all this work.