Aug 3, 2016 · setTimeout delays the execution of the code block by a specific time duration. Promises are an interface to allow async execution of code. A promise allows code to continue executing while you wait for another action to complete. Usually this is a network call.

The only exception is that in the main popular environments (browsers and Node), the resolution callback of a native Promise jumps the queue (more accurately, goes in a different higher-priority queue), see my answer here for details on that.

Jun 18, 2023 · Promises have a higher priority in the event loop queue compared to setTimeout callbacks. In other words, if a promise and a setTimeout callback are both scheduled at the same time, the promise...

Oct 20, 2021 · I know that a callback function inside setTimeout() will wait until the timer attached to it expires and the gets pushed into a callback queue. On the other hand, a promise, once fulfilled or rejected gets its callback pushed into a microtask queue, which has higher priority.

Dec 29, 2020 · Why an immediately resolved promise is processed faster than an immediate timer? Because of the event loop priorities dequeuing jobs from the job queue (which stores the fulfilled promises' callbacks) over the tasks from the task queue (which stores timed out setTimeout() callbacks).

Feb 14, 2023 · The event loop decides which task has highest priority from event queue. Since Promise has a higher priority compared to the setTimeout(), hence the output is “2” and “4”. Execution then moves back to the last statement of start () function and outputs “done”.

Nov 9, 2022 · And this is what makes the difference because the event loop which takes the async APIs from the callback queue and put it into the call stack (after the call stack is emptied) has a priority of dequeueing first the Job queue and then the Task queue.

Jun 14, 2024 · Micro-tasks have higher priority than the next task in the task queue. setTimeout : The setTimeout function schedules a function to be executed after a specified delay (in milliseconds).

Oct 26, 2022 · setTimeout() is the only thing that introduces asynchronous behaviour but the "async" activity of the browser in this case is to wait for the timeout to complete. Use web workers to run the time consuming calculations in the background.

Dec 23, 2021 · Because of the event loop priorities dequeuing jobs from the job queue (which stores the fulfilled promises’ callbacks) over the tasks from the task queue (which stores timed out setTimeout...