Macrotask and Microtask in JavaScript

Steve Mu
Oct 21, 2021


JavaScript engine execute two kinds of tasks in the event loop: macrotask and microtask.

One example of macrotask is event listener callback.

One example of microtask is the then in a promises.

Js engine event loop has two queues: one queue for the macrotask, another queue for the microtask.

It will execute one things from the macrotask queue, then execute everything on the microtask queue, then perform rerender.